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NET  BOOK— This  Book  is  supplied 
to  the  trade  on  terms  which  do  not 
admit  of  discount. 

THE  CHEMICAL  ENGINEER  PUBLISHING  CO, 


THE 

DESIGN    AND    EQUIPMENT 

OF  SMALL  CHEMICAL 

LABORATORIES 


BY 

RICHARD  K.  MEADE,  B.S., 

Editor  of  The  Chemical  Engineer, 

Author  of  Portland  Cement  and  The  Chemist' s  Pocket  Manual, 
Chemist,  Dexter  Portland  Cement  Co.,  etc. 


CHICAGO 
THE  CHEMICAL  ENGINEER  PUBLISHING  CO. 

355  DEARBORN  STREET 
1908 


Copyright   1908 

By 
The    Chemical    Engineer    Publishing    Company. 


PREFACE. 

It  very  often  happens  that  the  young  chemist,  perhaps  fresh 
from  college,  is  called  upon  to  design  and  equip  a  laboratory  when 
his  knowledge  of  how  it  is  to  be  done  is  rather  meagre.  The  ex- 
perienced chemist,  confronted  with  the  task,  can  usually  bring 
to  bear  upon  the  subject  sufficient  practical  knowledge,  gained 
from  other  laboratories  in  which  he  has  worked,  to  arrange  and 
equip  a  laboratory  which  will  meet  fully  his  requirements;  and 
can  do  so,  in  many  instances,  better  than  any  one  else  can  do  it 
for  him.  The  inexperienced  college  graduate,  on  the  other  hand, 
has  only  a  knowledge,  in  most  cases,  of  the  laboratory  of  the 
college  where  he  graduated.  Many  things  there  are  done  by 
means  which  he  cannot  command  in  his  new  position — for  in- 
stance, the  ventilation  of  the  hoods  and  rooms  is  perhaps  con- 
trolled by  mechanical  draft,  when  in  his  new  quarters  he  will 
not  have  the  power  to  run  fans;  or  the  gas  supply  may  be  that 
of  the  city,  when  his  new  laboratory  will  be  located  at  the  mines. 
To  these  young  chemists,  the  following  suggestions  on  the  design 
and  equipment  of  small  laboratories  are  made,  but  it  is  also  hoped 
that  even  experienced  chemists  will  find  in  them  some  points  of 
use  and  help. 

It  has  been  thought  best  throughout  the  book  to  mention  by 
name  the  firms  making  the  various  forms  of  apparatus  described. 
This  is  done  in  order  to  enable  the  reader  to  more  readily  obtain 
the  appliances  which  he  needs. 

We  wish  to  thank  those  manufacturers  who  have  loaned  cuts 
for  illustrating  the  various  special  devices  for  laboratory  use 
which  they  make. 

Part  of  this  book  appeared  as  a  series  of  articles  in  The 
Chemical  Engineer  during  1905.  These  have  been  carefully  re- 
vised and  much  new  matter  added. 

RICHARD  K.  MEADE. 
May  15,  1908. 


189918 


TABLE  OF  CONTENTS. 


Page. 

CHAPTER  I.— GENERAL  FEATURES i 

General  Arrangement. — Location. — Light  and  Ventilation. — 
Floor  Walls  and  Ceiling. — Heating  Appliances. — Interior  Ar- 
rangement.— Laboratory  for  Iron  and  Steel  Work. — Assay 
Laboratory. 

CHAPTER  II.— HOODS 7 

Simple  Hood. — Concrete  Top. — Gas  laps. — Canopy. — Light- 
ing the  Hood. — Mechanical  Ventilation  of  Hoods. 

CHAPTER  III.— SINKS  AND  WATER  SUPPLY 12 

Sink. — Water  Taps. — Drying  Apparatus. — Filtration  by 
Vacuum. — Vacuum  Pump. — Method  of  Using  Vacuum  for 
Filtering. — Stills,  .Extractors,  etc. — Miscellaneous. 

CHAPTER  IV.— DESKS 20. 

General  Arrangement. — Drawers. — Cupboards. — Shelves,  Re- 
agent Bottles. 

CHAPTER  V.— TABLE  AND  APPARATUS   FOR  RAPID  FIL- 

TRATIONS,  ETC 26- 

General  Features. — Wash  Bottles. 

CHAPTER  VI.— IGNITION  TABLE  AND    APPARATUS    FOR 

IGNITIONS 29; 

General  Features. — Crucible  Supports. — Blast  Lamp. — Air 
Blast. — Ignitions  in  a  Muffle  Furnace. — Platinum  Crucibles. 
— Porcelain  Crucibles. — Crucible  Tongs. — Miscellaneous. 

CHAPTER  VII.— TABLE  AND  APPARATUS  FOR  FILTRA- 

TIONS 37 

Burette  Stand. — Burettes. — Automatic  Zero  Burette. — Ap- 
pliances to  Aid  in  Reading  the  Burette. — Caps  for  Burettes. 
— Portable  Burettes  and  Solutions. — Pipettes. — Indicator 
Bottles. — Spot  Plates,  Etc. 

CHAPTER  VIII.— BALANCE  SUPPORT,  BALANCE  AND  AC- 
CESSORIES       46 

Brick  Pier  Support. — Iron  Column  Support. — Solid  Con- 
crete Support. — Shelf  Support. — Location  of  the  Balance  Sup- 
port.— Balance  Support  Bench. — The  Balance. — Assay  Bal- 
ances.— Weights. — Balances  for  Rough  Weighing. — Pans,  Etc. 

CHAPTER  IX.-HEATING  APPLIANCES 56 

General  Considerations.— Gasolene  Lamps. — Stoves. — Gas 
Machines. — Acetylene.— Burners. — Stoves  and  Hot  Plates. — 
Water  Baths  and  Air  Baths. 


TABLE    OP    CONTENTS. 

CHAPTER  X.— PREPARATION  OF  DISTILLED  WATER. . . 

Automatic  Stills. — Condensing  Steam  from  Boilers,  Etc. — 
Large  Stills. — Containers  for  Distilled  Water. 

CHAPTER  XL  — APPARATUS  FOR  ELECTROCHEMICAL 

ANALYSIS 73 

Use  of  the  Electric  Lighting  Current. — Gravity  Cells. — Stor- 
age Batteries. — Rheostat. — Arrangement  of  Cells. — Elec- 
trodes.— Stands. — Measuring  Instruments. — Rotating  Anode. 

CHAPTER  XII.— SAMPLING  APPLIANCES 86 

Mortar  and  Pestle. — Reducing  the  Bulk  of  Samples. — Crush- 
ers.— Agate  Mortar. — Mechanically  Operated  Agate  Mortar. — 
Gyratory  Muller. — Disc  Pulverizers. — Jar  Mill. 

CHAPTER  XIII.— ASSAY  FURNACES  AND  ACCESSORIES. . . .  102 

Gas  Fuel  Furnaces. — Liquid  Fuel  Furnaces. — Portable  Coal- 
Fired  Furnaces. — Permanent  Coal  Fired  Furnaces. — Crucibles, 
Scorifiers  and  Cupels. — Miscellaneous  Assay  Laboratory  Equip- 
ment. 

CHAPTER  XIV. — Miscellaneous  Laboratory  Equipment 119 

Aspirators. — Barometers.  —  Beakers. —  Carboys.  — Casseroles. 
Clamps.  —  Condensers.  —  Dishes. — Flasks. — Gases,  Drying  and 
Absorbing. — Gas  Generators. — Hydrometers. — Measuring  Ap- 
paratus.— Motors. — Rubber  Stoppers. — Rubber  Tubing. — Stir- 
rers,  Shakers,  Etc. — Thermometers. 


The    Design    and    Equipment    of 
Small  Chemical  Laboratories 


CHAPTER   I. 

GENERAL    FEATURES. 

In  designing  and  equipping  a  laboratory,  two  aims  must  be 
kept  always  in  mind — First,  to  promote  accuracy,  and  second,  to 
economize  time  and  labor.  Don't  make  the  mistake  of  sacrificing 
the  former  unnecessarily  to  the  latter,  but  always  save  time  and 
labor  when  possible  and  to  that  end  arrange  your  laboratory 
systematically.  Nothing  so  facilitates  rapid  work  as  having  a  place 
for  everything  and  doing  everything  in  that  place.  Where  space 
permits,  have  a  separate  table  for  carbon  combustions,  for  igni- 
tions, extractions,  evaporations,  for  titrations,  precipitations  with 
H2S,  distillations  and  for  electro-chemical  analysis,  filtrations  and 
various  and  sundry  special  tests. 

General  Arrangement. — The  location  of  the  laboratory  is 
usually  controlled  by  circumstances.  Sometimes  it  is  a  separate 
building,  sometimes  part  of  an  office  building  and  sometimes  a 
room  or  rooms  in  the  mill  or  factory  set  apart  for  the  purpose. 
If  a  separate  building  is  made  for  the  laboratory  special  features 
can  be  incorporated  in  its  design.  If,  however,  the  laboratory 
is  to  be  located  in  an  office  or  factory  building,  the  chemist  has 
usually  to  content  himself  with  what  he  can  get.  The  laboratory 
if  possible  should  consist  of  three  rooms,  two  of  which  should 
be  neatly  finished  inside  and  intended  for  the  analytical  work, 
and  the  third  of  which  may  be  merely  a  shed  room  to  be  used 
for  the  preparation  of  the  samples,  etc.  Where  only  one  room 
is  available  for  the  laboratory,  a  small  room  should  be  wainscotted 
off  a  corner  of  the  large  one  for  a  balance  room.  The  size  of 
this  balance  room  will  usually  be  controlled  by  that  of  the  large 
one.  If  permissible,  it  should  be  large  enough  for  a  desk,  book- 
case and  balance  table.  When  possible  it  should  always  include 
a  window;  if  not,  the  upper  half  of  the  sides  may  be  made  of 
glass.  Indeed,  even  when  a  window  is  present,  it  is  convenient 
to  do  this,  running  the  glass  low  enough  to  permit  of  any  one 


2  SMALL    CHEMICAL    LABORATORIES. 

seated  at  the  balance  or  desk  seeing  out  into  the  room.  In  this 
way  the  chemist  can  keep  track  of  things  while  weighing  or 
writing. 

Location. — If  a  choice  is  offered  in  locating  the  building  or 
selecting  a  room,  get  as  far  away  from  the  noise,  dirt  ajid  vibra- 
tion of  the  mill,  furnace  or  smelter  as  circumstances  will  permit. 
If  the  laboratory  is  to  be  located  in  an  office  building  of  two  or 
more  stories,  there  are  several  things  to  be  said  in  favor  of  locat- 
ing on  the  lower  floor.  The  chief  advantage  is  having  a  firm 
foundation  for  the  balance,  such  as  can  be  obtained  by  erecting 
a  short  brick  or  concrete  pier.  Its  disadvantages  are  usually 
annoyance  to  the  chemist  from  business  callers  for  the  office,  and 
annoyance  to  the  office  force  from  the  fumes  rising  from  the 
laboratory.  However,  properly  posted  signs  (using  foreign 
words  where  foreign  labor  is  employed)  in  the  hallways,  and 
good  ventilation  and  hoods  in  the  laboratory  will  usually  do  away 
with  these  annoyances. 

In  the  new  office  building  of  the  Dexter  Portland  Cement 
Co.,  the  laboratory  is  located  on  the  second  floor,  the  balance  room 
being  directly  over  a  heavy  concrete  fire  proof  vault  for  the  stor- 
age of  papers,  etc.  The  balances  are  mounted  on  concrete  pierv 
resting  on  the  vault  sides  and  roof  and  are  free  from  vibration, 
This  arrangement  is  excellent  and  is  one  which  can  be  followed 
in  many  places.  A  little  further  on  in  the  book  a  method  will 
be  described  for  mounting  balances  in  factory  buildings,  etc., 
where  they  are  subjected  to  jar  and  vibration. 

When  large  samples  have  to  be  reduced  either  by  hand  or 
mechanical  means  this  may  be  conveniently  done  in  the  basement 
of  the  office  building. 

Light  and  Ventilation. — The  laboratory  should  be  provided 
with  a  high  ceiling.  It  should  be  well  lit  either  from  windows 
or  a  skylight.  The  windows  should  come  near  the  ceiling,  so 
that  ventilation  can  be  secured  when  necessary  by  lowering  the 
upper  sash.  If  a  skylight  is  used  it  should  be  provided  with  ven- 
tilators. In  some  laboratories  artificial  ventilation  must  be  re- 
sorted to,  in  which  case  a  fan  (run  by  an  electric  motor)  located 
in  the  upper  part  of  one  of  the  windows  will  help  matters. 

Floor,  Walls  and  Ceiling. — The  floor  of  the  laboratory  should 
be  of  some  material,  hard  wood  is  best,  which  can  be  cleaned 
easily.  Concrete  and  tile  floors  are  very  trying,  for  the  analytical 


GENERAL  FEATURES.  3 

chemist  is  on  his  feet  so  much  that  he  is  apt  to  find  such  a  hard 
floor  very  fatiguing.  Concrete  floors  may  be  covered  with  felt 
or  corrugated  rubber  matting  which  can  be  easily  cleaned  and 
lessens  the  fatigue  of  those  standing  on  it.  Old  floors  full  of 
cracks  can  be  covered  with  oilcloth  or  linoleum.  This  latter  makes 
an  excellent  floor  covering,  as  it  can  be  easily  cleaned. 

The  walls  and  ceilings  should  be  finished  in  some  material 
such  as  hard  wall  plaster  or  cement,  which  is  not  readily  attacked 
by  acid  fumes.  If  the  wall  is  old  and  there  is  danger  of  grains 
of  sand  and  lime  dropping  in  beakers,  dishes,  etc.,  it  is  best  to 
cover  the  plaster  with  wall  paper.  This  should  be  of  a  light  pat- 
tern, so  as  not  to  darken  the  room.  It  is  probable  that  wood  is 
really  the  best  covering  for  the  walls  and  ceilings  of  the  labora- 
tory, as  it  is  not  attacked  by  acid  fumes.  Metal  ceilings  are  most 
objectionable,  and  all  exposed  metal  beams  should  be  well  pro- 
tected by  either  aluminum  paint  or  asphalt  varnish,  to  prevent 
corrosion  from  acid  fumes.  The  electric  wiring  should  always 
be  concealed  under  the  ceiling,  as  the  acid  fumes  rapidly  attack 
the  copper  wire,  and  the  lamp  socket  should  be  of  porcelain. 

Heating  Appliances. — For  heating  the  laboratory,  hot  water 
or  steam  is  to  be  preferred.  Air  is  objectionable  from  the  dust 
it  usually  carries.  If  the  laboratory  is  located  near  the  boilers, 
steam  for  heating  can  usually  be  obtained  from  these.  The  heat- 
ing apparatus  of  the  balance  room  should  not  be  too  near  the 
balances. 

Interior  Arrangement. — The  interior  arrangement  of  the  lab- 
oratory will  depend  somewhat  upon  the  kind  of  work  that  is  to^ 
be  done.  In  every  laboratory,  however,  there  should  be  a  hood, 
a  sink,  a  burette  table  and  a  bench  for  general  work.  In  all  the 
laboratories  which  the  writer  has  designed  he  has  set  aside  one 
special  stone  topped  table  on  which  to  place  the  blast  lamps  and 
burners  used  for  igniting  precipitates,  and  one  special  bench  to 
use  for  long  stemmed  funnels. 

The  insicle  arrangement  of  a  laboratory  can  best  be  illus- 
trated by  giving  plans  of  several  laboratories. 

Laboratory  for  Iron  and  Steel  Work. — Figure  I  shows  the  ar- 
rangement of  a  model  small  laboratory  for  iron  and  steel  work, 
consisting  of  a  one-story  frame  building  with  three  rooms.  The 
main  laboratory  is  20  x  19  feet,  the  balance  room  10  y  9,  and  the 
sample  room  10  x  n.  The  balanre  room  is  located  at  the  north- 


4  SMALL    CHEMICAL    LABORATORIES. 

east  corner,  giving  a  north  light  on  the  balances.  It  is  large 
enough  to  accommodate  a  bookcase,  roller  top  desk,  balance  table, 
and  the  necessary  chairs.  The  room  for  the  preparation  of  sam- 
ples contains  a  small  Bosworth  crusher  for  reducing  ores,  a  drill 
for  making  borings,  mortar,  pestle,  etc.  The  center  of  the  ana- 
lytical laboratory  is  occupied  by  the  hood.  The  details  of  this  are 
shown  in  Fig/4.  It  is  divided  into  two  compartments,  so  that 
silica  may  be  determined  in  one  side  by  Drown's  method,  while 
sulphur  is  being  determined  on  the  other  by  oxidation,  without 
danger  of  contaminating  the  latter  by  the  former.  The  sink  is  at 
one  end  of  the  double  hood  and  a  stone  top  ignition  table  at  the 


Fig.  1. — Plan  of  Small  Laboratory  for  Iron  and  Steel  Analysis. 

other.  Two  general  work  benches  face  the  two  hoods,  and  the 
ignition  table  is  flanked  on  one  side  by  the  burette  table  and  on 
the  other  by  the  table  for  carbon  combustions,  also  stone  topped. 
The  sink  has  a  table  provided  with  vacuum  on  each  side  of  it. 
The  advantage  of  the  arrangement  with  the  hood  in  the  center 
is  that  the  one  laboratory  is  practically  divided  into  two,  and 
two  men  can  easily  work  here  without  interfering  with  each 
other  in  any  way ;  each  hood  is  accessible  to  the  sink,  to  a  large 
work  bench,  and  to  the  table  with  the  vacuum  pumps. 

Fig.  2  shows  another  arrangement  of  a  laboratory  16  x  18 
feet.    Here  a  balance  room  has  been  cut  off  from  the  main  room 


GENERAL  FEATURES. 


by  a  wainscotted  partition.     It  is  7  x  8  feet  and  does  not  much 
more  than  accommodate  the  desk  and  balance  table  and  chairs 


Sa/. 


Des/f. 


'Case 


A//- 


Stood 


Fig.  2. — Plan  of  Small  Laboratory  with  Balance  Room  Partitioned  Off. 

for  the  two.    It  is  taken  from  a  corner  of  the  room  which  gives 
a  north  light,  and  as  it  takes  one  of  the  only  two  windows  of  the 


Furnace 


Fig.  3.— Plan  of  Small  Assay  Laboratory. 

room,  the  partition  is  of  glass,  to  help  light  the  main  laboratory. 
The  arrangement  is  evident  from  the  plan.     The  hood,  sink  and 


0  SMALL    CHEMICAL    LABORATORIES. 

large  bench  are  near  together,  and  most  of  the  work  is  done  here, 
leaving  the  other  benches  for  special  determinations.  As  the 
large  central  bench  is  double,  one  man  can  work  at  each  side  of 
it.  If  necessary,  the  hood  can  be  divided  into  two  compartments. 
Assay  Laboratory. — Fig.  3  shows  the  design  of  a  laboratory 
for  fire  assay  work.  This  consists  of  three  rooms,  an  office,  an 
assay  room  and  a  chemical  laboratory.  The  assay  room  contains 
a  crucible  furnace,  a  muffle  furnace  and  a  roaster  if  sulphide  ores 
are  assayed.  It  should  also  contain  a  coal  bin,  the  necessary  crush- 
ing and  grinding  machinery  for  preparing  samples,  a  rough  bal- 
ance for  weighing  the  fluxes  for  crucible  assays,  etc.  In  the  office 
will,  of  course,  be  the  button  balance,  the  pulp  balance  and  the 
analytical  balance,  besides  the  necessary  chairs,  desk,  cases,  etc. 
The  chemical  laboratory  should  be  provided  with  hood,  sink  and 
work  benches,  as  usual.  If  properly  equipped  this  laboratory 
will  take  care  of  a  great  deal  of  work. 


CHAPTER    II. 
HOODS. 

Upon  nothing  does  the  comfort  of  the  inmates  of  a  laboratory 
so  much  depend  as  upon  the  hood,  and  it  is  essential  that  this 
should  "draw"  well  in  order  to  carry  off  the  fumes. 


Fig.  4. — Simple  Laboratory  Hood. 
Scale  %"  =  1' 

Simple  Hood. — Fig.  4  shows  the  simplest  form  of  hood  and 
one  which  will  draw  best  of  all,  because  the  hot  gases  go  straight 
up  without  making  any  turns  or  bends.  A  hood  opening  into  a 
flue  warmed  by  chimney  gases,  even  though  the  hood  gases  make 
a  double  bend,  will  usually  draw.  Indeed,  for  most  work  it  is 


8  SMALL    CHEMICAL    LABORATORIES. 

unnecessary  to  encase  the  sides  of  a  hood  built  along  these  lines 
with  sliding  sashes.  The  writer  designed  some  years  ago  for  his 
use  a  hood  which  consisted  merely  of  a  stone  topped  table  over 
which  a  sloping  canopy  top  was  constructed,  like  a  hood  to  a 
blacksmith's  forge,  with  a  straight  flue  leading  up  through  the 
roof.  This  hood  was  not  connected  with  the  table  in  any  way, 
even  the  corner  posts  being  omitted.  It  stood  against  the  wall. 
The  table  top  measured  8x3  feet  and  the  rim  of  the  canopy  stood 
6  feet  2  inches  from  the  floor,  and  projected  3  inches  on  all  sides 
beyond  the  table  top.  This  hood  drew  beautifully,  and  even  sul- 
phide precipitations  could  be  made  in  it  without  even  an  odor 
of  hydrogen  sulphide  escaping  into  the  room. 

The  hood  shown  in  Fig.  4  can  be  readily  understood  from  the 
drawing.  The  dimensions  of  the  hood  are  6  feet  by  3  feet.  Its 
bottom  stands  32  inches  from  the  floor  and  the  rim  of  the  canopy 
top  is  6  feet  above  the  floor.  In  proportioning  a  hood,  the  height 
of  the  bottom  from  the  floor  should  be  such  that  the  hot  plates  to 
be  used  are  on  a  level  with  the  top  of  the  work  benches.  The  rim 
of  the  hood  canopy  should  be  high  enough  from  the  floor  not  to 
touch  the  operator's  head  when  he  stands  erect  under  it.  It  is 
usually  cheaper,  also,  to  take  stock-size  sash-frames  and  design 
the  hood  to  fit  these  rather  than  have  special  sash-frames  made 
to  fit  the  hood. 

The  hood  shown  is  meant  to  go  against  the  wall.  If  a  square 
hood  for  the  middle  of  the  room  is  desired,  the  front  and  sides 
will  be  alike. 

The  sides  of  the  hood  shown  are  closed  by  sliding  glass 
frames,  which  are  mounted  on  Pullman  spring  balances,  doing 
away  with  pulley  weights,  which  make  a  much  larger  and  more 
cumbersome  framework  necessary.  In  this  hood  the  upper  frame- 
work is  made  to  merely  rest  upon  the  table  top  if  this  is  of  stone ; 
otherwise  it  can  be  fastened  to  the  top. 

The  hood  shown  in  Fig.  4  is  made  with  a  table  for  a  base. 
Instead  of  this,  the  hood  can  of  course  be  mounted  on  a  press  or 
cupboard  using  the  latter  for  storage  of  acids,  apparatus,  etc. 

Concrete  Top. — The  writer  having  had  considerable  experi- 
ence with  concrete,  the  idea  of  covering  the  floor  of  the  hood  with 
concrete  instead  of  using  a  stone  slab  occurred  to  him  some  years 
ago.  Where  this  is  done,  it  is  only  necessary  to  put  a  wood  top 
of  rough  plank  on  the  table,  making  this  top  three  inches  nearer 


HOODS.  9 

to  the  floor  than  the  completed  top  is  to  be.  Then  put  on  the  super- 
structure and  canopy  part  of  the  hood.  Next  finish  off  the  rough 
edges  of  the  table  top  and  fasten  tightly  to  this  with  thin  screws 
a  wooden  rail,  whose  top  is  3  inches  from  the  rough  wooden  top. 
Then  fill  in  to  the  top  of  this  wooden  rail  with  concrete.  The 
best  mixture  for  this  purpose  is  limestone  screenings,  using  one 
part  of  cement  to  3  of  limestone  screenings  passing  through  a 
^8-inch  screen.  The  advantage  of  using  limestone  screenings  in 
place  of  sand  is  that  any  acids  spilled  in  the  hood  will  attack  both 
the  cement  particles  and  those  of  the  limestone,  leaving  an  even 
surface ;  while  if  sand  is  used,  only  the  cement  is  attacked,  leaving 
a  rough,  uneven  surface.  The  cement  sand  mixture  is  also  more 
porous  than  the  cement  limestone.  After  the  concrete  is  hard  the 
rail  can  be  removed,  the  screws  greatly  facilitating  this.  Another 
very  serviceable  floor  for  a  hood  js  sheet  lead.  This  can  be  cut 
to  fit  the  wood  bottom,  allowing  3  or  4  inches  for  turning  over  and 
under  the  sides.  One-sixteenth  inch  lead  is  thick  enough  and  can 
be  easily  worked.  The  hood  may  also  be  lined  with  tiles  or  with 
24 -inch  asbestos  board.  The  concrete  mixture,  however,  is  much 
cheaper  than  the  latter  and  is  far  preferable  to  it. 

Gas  Taps. — The  gas  taps  for  the  hood  should  run  around  the 
front  of  the  hood,  as  it  is  very  inconvenient  to  reach  over  hot  plates, 
etc.,  to  turn  them  out ;  and  at  times  it  may  be  necessary  to  control 
the  gas  supply  from  outside  the  glass  doors.  The  gas  taps  are 
usually  placed  as  they  are  in  Fig.  4,  the  rubber  tubing  passing  to 
the  interior  of  the  hood  through  holes  bored  in  the  hood  floor.  If 
this  latter  is  to  be  of  concrete,  before  putting  in  this,  cut  4  inch 
pieces  of  iron  or  brass  pipe  y^  inch  inside  diameter  and  set  in 
holes  bored  through  the  rough  wood  bottom  so  that  their  tops  are 
level  with  that  of  the  wooden  rail.  Another  plan  is  to  pass  the 
tubing  over  the  edge  of  the  hood  floor,  in  which  event  notches 
must  be  cut  out  of  the  sashes ;  or,  since  some  air  must  always  be 
admitted  to  the  hood  to  form  a  current  to  sweep  the  fumes  up  the 
flue,  a  block  or  stop  may  be  put  in  the  frame  for  the  sashes  so 
that  when  closed  the  bottom  of  the  sash  is  one  or  two  inches  from 
the  stone  slab.  This  is  usually  only  done  when  a  stone  top  which 
has  not  been  bored  is  used  as  a  bottom.  Where  the  top  is  of  con- 
crete the  gas  piping  may  be  first  fitted  and  laid  on  the  wooden 
top,  the  concrete  then  being  placed  over  it,  leaving  only  the 
tops  sticking  up,  as  in  Fig.  5. 


10 


SMALL    CHEMICAL    LABORATORIES, 


Canopy. — In  the  hoods  shown,  the  canopy  part  is  built  of  l/2 
inch  matched  and  grooved  lumber.  This  is  light  and  is  not  at- 
tacked by  fumes.  It  is  so  far  away  from  the  burners  as  to  be 
in  no  danger  of  catching  fire.  Where  the  room  is  not  very  well 
lighted  this  top  may  of  course  be  made  of  glass ;  in  which  case,  it 
is  perhaps  best  to  run  the  framework  up  to  the  ceiling  and  merely 
add  a  row  of  sashes,  making  a  sort  of  glass  box.  The  plastered 
ceiling  should  be  covered  with  wood,  however,  as  it  is  almost 
sure  to  be  attacked  by  the  fumes,  dropping  sand  and  lime  into 
solutions,  etc.,  evaporating  below. 

Lighting  the  Hood. — If  the  laboratory  is  lit  with  electric 
lights,  a  few  of  these  should  be  put  in  the  hood.  They  should  be 
held  in  a  round  porcelain  base  socket,  without  key,  screwed  to  the 
frame,  the  wiring  all  being  concealed  and  the  lights  turned  on 


Fig.  5.— Arrangement  of  Gas  Taps  in  Concrete. 

and  off  by  a  switch  on  the  outside.  The  metal  work  where  the 
globe  and  socket  join  should  be  wrapped  with  insulating  tape  so 
that  no  metal  is  exposed.  If  gas  is  used,  an  ordinary  fish  tail 
burner  in  the  centre  of  the  hood,  directly  underneath  the  wood 
flue,  will  not  only  give  the  necessary  light  but  will  also  help 
along  the  draft  of  the  hood. 

Mechanical  Ventilation  of  Hoods. — It  occasionally  happens 
that  gases  given  off  in  the  hood  are  heavier  than  air  and  will  not 
rise.  In  this  event,  the  gases  must  be  drawn  off  at  a  level  with 
the  hood  floor,  by  a  small  fan  directly  connected  with  a  motor. 
Such  a  hood  should  be  provided  with  a  small  sliding  ventilator 
at  the  top,  which  may  be  opened,  admitting  fresh  air  into  the 
hood  when  the  fan  is  running.  It  is  hardly  necessary  to  say  that 
such  a  hood  shoXild  have  sides. 

Where  a  hood  connects  with  a  flue  in  the  walls  of  the  build- 


HOODS.  II 

ing  it  is  sometimes  hard  to  get  a  draft,  particularly  in  summer 
time  when  the  flue  is  cold.  In  such  cases  a  lighted  gas  burner 
placed  just  inside  the  flue  will  help  matters.  The  flue  should  also 
draw  only  from  the  hood.  Draft  can  of  course  always  be  secured 
by  fans;  these  are  rapidly  corroded  by  acid,  however,  and  are 
expensive  to  operate.  Where  their  use  is  necessary  and  fumes 
corroding  metal  are  present,  the  writer  suggests  washing  the 
gases  by  passing  them  up  through  a  cylinder  formed  by  a  length 


Co/w. 

^//-; 


T 

( 

-  HI  —  >   s 

.^iti  **""-"-•"'*  —  i 

Fig.  6. — Injector  for  Ventilating  Hoods. 

or  two  of  sewer  pipe.  This  is  to  be  filled  with  coke,  kept  wet  by 
water  trickling  over  it,  in  order  to  wash  out  the  corrosive  gases, 
before  they  come  in  contact  with  the  fan.  The  acid  water  could 
then  be  caught  in  a  lead  or  earthen-ware  receptacle  at  the  bottom 
of  the  pipe  and  allowed  to  go  to  waste  by  drawing  off  occasion- 
ally. When  high  pressure  air  is  available,  a  small  hood  may  be 
ventilated  by  allowing  this  to  flow  through  a  small  opening  creat- 
ing suction,  see  Fig.  6,  on  the  principle  of  an  injector. 


CHAPTER   III. 


SINKS   AND   WATER    SUPPLY. 

In  most  college  laboratories  and  in  some  large  industrial 
ones  the  sinks  are  located  in  the  middle  or  at  the  ends  of  the 
work  benches.  In  a  small  laboratory,  however,  it  will  be  found 
more  convenient  to  have  a  separate  table  for  the  sink  and  it  will 
save  plumbing  to  fit  this  table  up  for  filtration  by  vacuum,  dis- 
tillations, etc. ;  in  short  for  all  the  operations  of  the  laboratory 
requiring  water.  Figure  7  shows  such  a  table.  It  is  12  feet  long 


Pig.  7.— Sink  and  Table. 

and  3  feet  wide.  Its  top  is  33  inches  from  the  floor.  It  is  pro- 
vided with  a  vacuum  pump,  a  sink  3x2  feet,  two  water  taps,  a 
drain  board,  shelves  for  clean  beakers  and  one  for  drying  flasks, 
etc.,  water  taps  and  waste  pipe  for  condensers  and  for  the  still  for 
furnishing  distilled  water,  and  gas  taps  for  these  latter. 

Sink. — The  sink  is  placed  four  feet  from  one  end  of  the 
table,  leaving  a  space  of  table  of  this  length  on  the  right,  for 
filiations  by  vacuum;  and  on  the  left  for  drying  beakers  and 
for  standing  apparatus  to  be  washed,  etc. 

The  sink  itself  may  be  of  galvanized  iron,  zinc  or  enameled 
iron.  The  latter  is  to  be  preferred.  Wood  also  makes  a  very 
good  sink,  but  it  is  hard  to  make  one  out  of  it  which  does  not 


SINKS  AND  WATER  SUPPLY.  13 

leak.  The  writer  at  one  time  had  a  large  wooden  sink,  4  ft.  x  3 
ft.,  in  his  laboratory  which  gave  excellent  service.  In  order  to 
prevent  drying  and  consequent  leaking,  the  waste  pipe  was  so 
arranged  as  to  keep  about  an  inch  of  water  in  the  bottom  of  the 
sink  all  the  time.  The  usual  objection  to  metal  sinks  is  the 
corrosion  due  to  acids,  and  the  fact  that  glassware  must  be  care- 
fully handled  around  them,  as  a  very  light  tap  against  the  bottom 
of  a  metal  sink  is  sure  to  result  in  a  broken  beaker  or  flask.  A 
sheet  of  corrugated  rubber  matting  or  a  small  rubber  door  mat 
laid  in  the  sink  will  save  much  apparatus.  Underneath  the  sink 
is  as  good  a  place  as  any  for  a  large  stoneware  jar  in  which  to 
pour  waste  acids  and  filter  papers.  This  jar  is  to  be  emptied  daily 
by  the  janitor  and,  if  used,  will  save,  many  plumbers'  bills  for 
renewing  the  waste-pipe. 

As  the  sink  table  is  3  feet  wide  and  the  sink  is  but  two,  the 
latter  should  be  so  placed  in  the  former  as  to  be  about  four  inches 
from  the  front  of  the  table.  This  space,  before  and  behind, 
should  be  boxed  up  and  the  edges  of  the  boards,  lapping  over 
the  sink,  nicely  rounded.  In  the  drawing,  the  waste-pipe  is  shown 
straight  without  the  usual  S-shaped  trap.  When  the  waste-pipe 
does  not  lead  into  the  same  sewer  as  the  toilet  room,  this  trap 
can  be  omitted;  and,  if  it  is  done,  will  save  repairs,  as  acids  are 
almost  sure  to  find  their  way  into  the  sink  and,  if  the  acid  water 
lies  in  the  bend  of  the  trap,  it  will  in  time  eat  a  hole  in  this.  Lead 
is  to  be  preferred  to  iron  for  the  waste-pipe  as  the  less  readily 
attacked  by  acids. 

Water  Taps. — In  the  illustration  of  the  sink  table  a  peculiar 
form  of  water  tap  is  shown  over  the  sink.  This  is  one  made  by 
Thos.  Saville,  Philadelphia,  Pa.  An  ordinary  lever  tap  may  also 
be  used.  The  advantage  of  this  form  is  that  the  water  can  be 
turned  on  full  with  a  single  motion  of  the  hand  or  shut  off  equally 
easily.  It  will  be  found  of  advantage  to  place  a  few  inches  of 
rubber  tubing  on  the  end  of  at  least  one  of  the  taps.  This  not 
only  permits  the  stream  of  water  being  directed  in  any  direction 
but  if  the  force  of  its  flow  from  the  tap  is  considerable  it  deadens 
this  somewhat.  The  taps  should  stand  at  least  six  inches  forward 
of  the  rear  end  of  the  sink  and  their  tips  should  be  about  18 
inches  from  the  bottom. 

Drying  Apparatus. — A  board  for  drying  beakers,  etc.,  should 
be  located  to  one  side  of  sink.  In  the  table  shown,  this  board  is 


14  SMALL    CHEMICAL    LABORATORIES. 

2  ft.  x  3  ft.,  extending  all  the  way  across  the  table.  It  is  corru- 
gated like  a  wash  board,  all  the  grooves  radiating  from  the  sink 
so  as  to  drain  the  water  into  this.  Above  the  board  are  shelves 
for  clean  dry  beakers.  If  thought  desirable,  these  can  be  made 
into  a  cupboard  by  adding  doors.  Above  the  sink  is  a  shelf  bored 
with  holes  of  various  sizes  for  drying  flasks,  pipettes,  etc.,  as 
shown  in  the  cut. 

Casseroles  are  much  used  in  some  iron  and  steel  laboratories 
in  place  of  beakers.  For  drying  these,  a  board  with  pegs,  inclined 
about  15°  from  the  vertical,  placed  behind  and  so  as  to  drain  into 
the  sink,  will  be  found  useful.  The  pegs  should  be  in  pairs,  in  a 
row,  and  placed  so  that  the  casserole,  laying  face  to  the  board, 
handle  downward,  has  a  peg  on  each  side  of  the  handle.  The 
pegs  should  be  about  four  inches  long  and  the  rows  should  be 
no  nearer  together  than  the  diameter  of  the  greatest  casserole  in 
use.  Each  pair  of  pegs  should  be  the  same  distance  apart  as  the 
rows,  and  the  individual  pegs  of  the  pair  should  be  about  il/2  or 
2  inches  apart. 

Filtration  by  Vacuum. — The  vacuum  or  suction  arrangement 
shown  has  four  openings  and  hence  four  filtrations  can  be  made 
at  the  same  time.  If  less  than  this  number  are  ample  for  the  work 
to  be  done,  the  table  may  be  shortened  accordingly.  In  an  iron 
and  steel  laboratory,  where  many  samples  of  pig  iron  are  analyzed 
for  silicon,  sulphur,  etc.,  four  will  not  be  found  too  many,  as  one 
of  them  may  be  needed  for  a  reductor  and  the  rest  will  be  kept 
in  use  for  filtering  off  graphite,  etc.,  from  the  solution  of  the  pig 
iron.  Since  three  or  four  filtrations  can  usually  be  carried  out 
as  rapidly  as  one,  it  will  save  time  to  provide  means  for  making 
this  number  simultaneously. 

Vacuum  Pump. — The  form  of  vacuum  pump,  filter  pump  or 
aspirator  shown  in  the  illustration  is  that  of  Chapman..  This 
pump  is  small  but  effective.  Figure  8  shows  the  details  of  its 
construction.  It  is  made  in  three  sizes.  A  No.  2  pump  will  be 
of  ample  capacity  to  take  care  of  four  filtrations  and  the  smallest 
size,  No.  i,  will  furnish  vacuum  for  one  or  two  filtrations.  It 
can  be  obtained  with  a  threaded  coupling  to  fit  a  threaded  faucet 
or  with  a  smooth  coupling  for  a  plain  faucet.  The  former  is 
much  to  be  preferred  and  is  essential  if  the  water  pressure  to  be 
used  is  great.  The  threaded  coupling  has  a  milled  ring  around  it 
so  the  pump  can  be  readily  removed  from  the  faucet  for  cleaning. 


SINKS  AND  WATER  SUPPLY.  15 

This  is  sometimes  necessary,  as  it  often  becomes  stopped  up  with 
sticks,  leaves  and  other  trash  in  the  water.  The  greater  water 
pressure  which  is  at  hand  the  more  perfect  vacuum  can  be  ob- 
tained. A  fair  suction  will  be  secured,  however,  from  a  head  of 
water  such  as  would  result  from  a  tank  placed  on  the  laboratory 
roof.  Another  form  of  air  pump  is  that  of  Richards.  This  also 
is  very  efficient  and  is  made  in  two  sizes.  Still  another  form  has 
a  vacuum  gauge  attached,  but  these  cost  considerably  more.  If 
it  is  desired  to  measure  the  vacuum,  it  may  be  done  by  means  of 
a  long  U  tube,  about  30  inches  high,  half  full  of  mercury.  One 
end  of  this  is  attached  to  the  pump  and  the  vacuum  is  measured 
by  the  difference  between  the  levels  of  the  mercury  in  the  two 
limbs  of  the  tube.  If  wished  this  mercury  tube  may  be  fastened 


Fig.  8. — Chapman's  Vacuum  Pump. 

to  the  wall  behind  the  sink  table  and  permanently  attached  to 
one  of  the  openings  of  the  vacuum  line. 

As  these  little  pumps  are  somewhat  apt  to  let  water  pass 
back  into  the  air  line,  if  the  water  supply  is  suddenly  cut  off  or 
the  pump  clogs,  it  is  safest  to  place  a  trap  between  the  pump 
and  the  air  line.  This  may  be  merely  a  pint  bottle  provided  with 
a  double  perforated  stopper,  through  one  of  whose  holes  a  piece 
of  glass  tubing  passes  nearly  to  the  bottom  of  the  bottle  and 
through  the  other  of  whose  holes  a  shorter  piece  of  tubing  reaches 
just  below  the  stopper.  A  more  durable  form  of  trap  is  made  of 
a  piece  of  pipe  3  inches  in  diameter  and  6  inches  long  capped  at 
both  ends  to  form  a  small  drum.  Two  pieces  of  %-inch  pipe  are 
fitted  into  this,  one  reaching  nearly  to  the  bottom  of  the  drum  and 
the  other  just  inside  the  cap.  The  long  pipe  or  tubing  connects 
with  the  pump  and  the  short  one  with  the  air  line.  This  latter 


16  SMALL    CHEMICAL    LABORATORIES. 

joint  if  the  drum  is  used  should  be  made  by  a  threaded  pipe 
fitting,  and  the  connection  between  the  drum  and  the  pump 
by  a  piece  of  heavy  walled  rubber  tube,  as  shown  in  Fig.  7,  to 
facilitate  disconnecting  the  pump  for  cleaning. 

Where  a  powerful  suction  is  required  and  there  is  only  a 
light  head  of  water,  these  filter  pumps  may  be  operated  by  steam 
or  compressed  air.  Schutte  &  Koerting  Co.,  Philadelphia,  Pa., 
make  a  very  powerful  filter  pump  to  be  operated  by  steam  which 
they  call  the  "Universal  Steam  Jet  Laboratory  Exhauster."  This 
with  vacuum  gauge  attached  is  listed  by  the  manufacturers  at 
$10.00.  It  requires  for  operation  a  volume  of  steam  equivalent 
to  an  evaporation  of  12  pounds  of  water  per  hour.  When  there 
is  a  head  of  water  available,  however,  the  writer  knows  of  nothing 


Fig.  9.— Flask  Equipped  with  Funnel  and  Cone  for  Filtration  by  Suction. 

better  for  filtrations  by  suction  than  the  Chapman  filter  pump 
first  mentioned. 

Method  of  Using  Vacuum  for  Filtering. — For  use  with  these 
pumps  in  filtering  nothing  is  more  serviceable  than  a  thick  walled 
Erlenmeyer  flask  fitted  with  a  two-hole  rubber  stopper.  A  60° 
short,  thin-stemmed  funnel,  of  exact  angle,  passes  through  one  hole 
of  the  stopper  and  a  piece  of  glass  tubing  bent  at  right  angles 
through  the  other,,  reaching  just  below  the  stopper.  A  perforated 
platinum  cone  fits  in  the  funnel  and  prevents  the  filter  paper  from 
being  torn  by  the  suction.  Figure  9  shows  the  completed  appar- 
atus. A  special  form  of  Erlenmeyer  flask  can  be  obtained,  having 
a  tube  inserted  in  the  neck. and  made  of  very  heavy  glass,  at  a 
slightly  increased  cost.  This  is,  however,  but  little  more  conven- 
ient and  indeed  has  some  disadvantages  over  the  simpler  form. 
In  using  Erlenmeyer  flasks,  the  filtrate  has  often  to  be  transferred 


SINKS  AND  WATER  SUPPLY. 


to  a  beaker.  In  order  to  obviate  this  the  bell-jar  and  ground 
glass  plate  shown  in  Fig.  10  can  be  used.  For  filtering  barium 
sulphate  the  Gooch  crucible  is  very  useful.  This  requires  suc- 
tion and  consists  of  a  flat  bottomed  perforated  crucible  provided 
with  a  cap,  see  Fig.  n.  The  perforated  crucible  is  placed  in  one 
end  of  a  piece  of  soft  rubber  tubing  of  a  large  bore,  the  other 
end  of  which  is  stretched  over  a  small  funnel  passing  into  the 
Erlenmeyer  flask,  through  a  rubber  stopper,  see  Fig.  12.  The 
method  of  using  is  as  follows :  Pour  a  little  prepared  asbestos 
(purified  by  washing  with  hot  concentrated  hydrochloric  acid) 
suspended  in  water  into  the  crucible  and  attach  the  suction  to 


Fig.   10.— Bell-Jar  and  Plate  for    Fig.  11.— Gooch    Fig.  12.— Gooch  Crucible 
Filtration  by  Suction.  Crucible.  Ready  for  Use. 

the  flask.  The  asbestos  at  once  forms  a  thick  felt  over  the  bot- 
tom of  the  crucible,  which  by  using  the  suction  may  be  readily 
washed  with  water.  After  washing,  suck  as  dry  as  possible  with 
the  pump.  Remove  from  the  funnel,  detach  any  pieces  of  asbestos 
that  may  be  on  the  outside  of  the  bottom  of  the  crucible,  cap, 
ignite  and  weigh.  Remove  the  cap,  attach  to  the  funnel  as  before, 
apply  the  suction  and  pour  the  liquid  to  be  filtered  through  the 
crucible,  wash  cap,  dry,  if  necessary,  ignite  and  weigh  as  before. 
The  Gooch  crucible  is  made  of  either  porcelain  or  platinum ;  those 
of  the  former  material  have  no  cap,  and  are  made  either  with  a 
permanent  bottom,  or  with  a  movable  porcelain  or  platinum  plate, 
which  rests  on  a  small  border,  in  place  of  a  bottom. 


IS 


SMALL    CHEMICAL    LABORATORIES. 


When  the  filtrates  are  to  be  discarded  and  many  filtrations 
are  made  every  day,  such  as  silicon  in  pig  iron,  it  will  be  found 
more  convenient  to  filter  into  a  large  bottle,  instead  of  a  small 
flask,  doing  away  with  the  necessity  of  emptying  the  receiver 
after  each  filtration. 

Stills,  Extractors,  Etc. — The  left  end  of  the  table  shown  in 
the  cut  is  reserved  for  distillations  and  is  accordingly  provided 
with  gas  as  well  as  water.  Where  many  distillations  or  extrac- 
tions have  to  be  made,  however,  a  larger  table  may  be  found 
necessary.  Figure  13  shows  a  compact  still  for  nitrogen  deter- 
minations, which  will  allow  of  six  distillations  being  carried  on 
at  once,  and  which  will  fit  this  table  space  nicely.  Stutzer's  ap- 


Fig.    13.— Apparatus    for    Nitrogen    Determination. 

paratus  for  extractions  is  also  very  compact  and  is  used  in  the 
German  agricultural  experiment  station  at  Bonn.  It  will  take 
care  of  six  extractions.  Both  forms  are  made  by  Messrs.  E.  H. 
Sargent  &  Co.,  of  Chicago. 

The  cooling  water  from  the  condensers  runs  down  into  a 
waste  pipe,  which  is  brought  up  flush  with  the  top  of  the  desk, 
behind  the  drawers,  and  which  connects  with  the  drain  pipe  of 
the  sink,  as  shown  in  Fig.  7. 

Where  extractions  have  to  be  frequently  made  with  ill  smel- 
ling liquids,  such  as  carbon  bisulphide,  it  is  well  to  either  partition 
this  end  of  the  table  off  to  form  a  hood  or  else  to  extend  the 
water  and  was^e  line  into  the  hood.  Where  extractions  are  made 


IQ 

with  very  volatile  or  inflammable  liquids,  it  is  safest  to  do  the 
heating  with  electric  stoves.  Several  forms  of  these  will  be  men- 
tioned later  on. 

Miscellaneous. — The  sink  table  as  illustrated  is  provided  with 
drawers  and  is  boxed  up  to  form  a  closet  for  storage  of  apparatus. 
To  prevent  trash,  etc.,  being  brushed  into  the  latter  when  the 
floor  is  swept,  the  floor  of  the  closet  should  be  at  least  3  inches 
above  that  of  the  room. 

The  top  of  the  table  may  be  of  wood,  stone,  slate,  concrete  or 
sheet  lead.  Two-inch  white  pine  board  makes  a  good  cheap  top. 
When  this  becomes  acid  scarred  it  can  be  covered  with  oilcloth 
or  the  boards  turned,  exposing  the  lower  surface,  or  renewed 
entirely.  The  desk  itself  should  be  filled  and  varnished  or  primed 
and  painted.  The  top,  however,  if  of  wood  should  not  be  treated 
in  any  way  but  should  be  left  just  as  it  is. 

It  is  well  to  have  on  the  water  line,  somewhere  easily  acces- 
sible, a  valve  with  about  five  or  ten  feet  of  good  garden  hose, 
with  nozzle  attached,  for  fire  protection.  This  will  be  found 
cheaper  than  the  hand  grenades  and  equally  serviceable  for  put- 
ting out  small  fires. 


CHAPTER   IV. 
DESKS. 

General  Arrangement. — The  one  thing  about  a  mill  labora- 
tory which  is  very  similar  to  the  college  laboratory  is  the  desk 
or  work-bench  for  general  operations  which  is  present  in  one 
form  or  another  in  every  laboratory.  If  the  desk  is  to  be  placed 
in  the  middle  of  the  room,  it  is  usually  a  double  desk;  if  against 
the  sides  of  the  wall,  it  is,  of  course,  a  single  desk.  The  size  will 


Fig.    14.      Laboratory   Desk — Front   Elevation. 

vary  to  suit  the  space  which  it  is  to  occupy.  Particularly  is  this 
true  with  respect  to  length.  With  regard  to  its  width,  the  latitude 
is,  of  course,  not  so  great.  Nothing  is  gained  by  having  a  single 
desk  over  three  feet  wide,  or  a  double  desk  over  six  feet  wide; 
nor  would  it  be  advisable  to  make  a  double  desk  less  than  forty- 
five  inches  wide.  The  height  from  the  floor  may  vary  with  the 
ideas  of  the  user;  the  usual  height,  however,  is  from  34  to  38 
inches.  The  writer  has  found  36  inches  a  good  height.  The 
general  work-bench  is  usually  made  with  closets  and  drawers. 
Some  desks  are  made  with  the  drawer  part  projecting  beyond  the 


DESKS.  11 

closets.  This  has  the  advantage  of  making  the  closet  less  deep 
and  consequently  allowing  several  shelves  to  be  put  in  the  latter. 
Figures  14  and  15  show  a  desk  such  as  the  writer  has  gen- 
erally used,  which  is  modeled  somewhat  after  those  with  which 
most  students  are  familiar  in  the  college  laboratories,  and  Fig. 
1 6  shows  this  same  desk  with  the  drawer  part  projecting  beyond 
the  closets.  Its  dimensions,  in  this  particular  case,  are  7  feet  by 
5  feet  and  it  is  36  inches  in  height.  It  has  five  drawers  on  each 
side — two  narrow  drawers  for  watch  glasses,  filter  papers,  evap- 
orating dishes  and  such  flat  apparatus ;  one  deep  drawer  for  large, 


Fig.   15. — Laboratory  Desk— End  Elevation. 

bulky  articles;  and  two  wide  shallow  drawers  for  burettes,  glass 
tubing,  and  long  flat  articles.  If  the  desk  is  desired  longer  than 
this,  it  can,  of  course,  be  lengthened  by  the  addition  of  another 
set  of  drawers  and  cupboards. 

Drawers. — There  is  usually  more  or  less  inconvenience  in 
pulling  drawers  in  and  out,  from  their  binding  on  the  sides-.  This 
is  particularly  annoying  when  the  drawer  is  full  of  glassware,  as, 
breakage  is  likely  to  occur  from  the  sudden  jar  used  to  force  it 
in  or  pull  it  out.  Figure  17  shows  an  arrangement  which  will 
prevent  this.  It  consists  in  fastening  a  narrow  strip  of  well- 
seasoned  board,  B,  along  the  bottom  of  the  drawer,  A,  and  fast- 


22 


SMALL    CHEMICAL    LABORATORIES. 


ening  to  the  frame  of  the  desk  two  other  narrow  strips,  C/  C" 
one  on  each  side  of  the  strip  on  the  drawer.  These  two  strips 
form  a  groove  in  which  the  other  one  runs  and  in  this  way  the 
drawer  is  always  kept  in  the  proper  position  to  slide  in  and  out 
easily. 

The  drawers  can  be  cut  up  into  partitions  for  different  sizes 
of  watch  glasses,  filter  papers,  evaporating  dishes,  etc.  If  no  safe 
is  at  hand  in  which  to  store  the  platinum,  one  of  the  top  drawers 
of  the  bench  may  be  provided  with  a  lock  and  key  and  used  for 
this  purpose.  In  this  case,  instead  of  an  ordinary  bottom  it  should 


Fig.   17. — Guide  for  Drawers. 


Fig.   16.— Laboratory  Desk  with 
Projecting  Drawers. 

have  a  piece  of  two-inch  board  fitted  in.  In  this  are  to  be  bored 
holes  which  exactly  fit  the  various  crucibles,  dishes,  etc.,  in  use  in 
the  laboratory.  The  holes  for  the  crucibles  need  not  be  gouged 
out  just  to  fit  the  crucibles  but  may  be  bored  with  brace  and  bit 
of  such  size  that  the  crucible  will  fit  in  them  snugly.  Alongside 
of  the  hole  for  the  crucible  should  be  cut  a  narrow  deep  slot  for  its 
lid.  This  is  a  very  satisfactory  way  of  keeping  platinum,  as  each 
crucible  has  its  place  and  can  not  roll  around  in  the  drawer, 
thereby  getting  out  of  shape. 

In  the  drawers  designed   for  such  apparatus  as  U-tubes, 


DESKS.  23 

CaCl2  tubes,  etc.,  it  will  be  well  to  have  rows  of  pegs  about  three 
or  four  inches  apart,  and  il/2  to  2  inches  high;  the  tubes,  etc., 
can  then  be  laid  in  among  these  in  such  a  way  as  to  keep  them 
from  rattling  around  every  time  the  drawer  is  opened,  thereby 
preventing  breakage. 

Cupboards. — The  floor  of  the  cupboard  should  be  three  inches 
above  the  floor  of  the  laboratory  to  prevent  dust,  etc.,  being  swept 
into  the  former.  Shelves  can,  of  course,  be  added  if  desired.  In 
the  desk  shown  in  Fig.  15  there  is  a  shelf  midway  between  the 
floor  and  the  cupboard.  In  a  desk  made  as  deep  as  this,  one  shelf 
is  all  that  can  well  be  added.  In  a  narrower  desk,  several  shelves 
can  be  added,  as  it  is  not  necessary  to  reach  back  so  far  for  the 
apparatus.  Instead  of  having  the  doors  of  this  cupboard  arranged 
to  open  outward,  as  they  are  in  the  cut,  they  can  be  fixed  to  slide 
by  each  other  in  grooves. 

Shelves. — The  reagent  shelf  should  be  at  least  six  inches  wide 
for  the  single  desk  and  about  ten  to  fourteen  for  the  double  desk. 
A  six-inch  shelf  will  hold  a  five-pound  reagent  bottle  or  a  five- 
pint  acid  bottle.  If  wished,  the  bottom  shelf  may  be  six  or  eight 
inches  wide,  and  the  next  an  inch  or  so  less.  If  gas  is  on  the  table, 
the  bottom  shelf  may  be  raised  a  little  above  the  desk  and  the 
space  between  the  two  filled  in  to  make  a  sort  of  stop,  as  shown  in 
Fig.  15,  so  that  Bunsen  burners  cannot  be  carelessly  pushed  under 
the  shelves  and  set  them  on  fire.  In  most  commercial  laboratories 
where  special  tables  can  be  provided  for  each  operation,  gas  may 
not  be  needed  on  the  general  work  table.  If  desired,  however,  it 
can  be  run  either  along  the  front  of  the  table  just  above  the 
drawers,  or  along  the  back  of  the  first  reagent  shelf ;  or  this  shelf 
may  be  raised  six  inches  from  the  table  and  the  gas  pipe  run  un- 
der it. 

If  it  is  desired  to  set  five-pint  acid  bottles  on  the  shelf,  it  must 
be  at  least  14  inches  from  the  one  above  it.  Nothing  is  gained  by 
running  the  reagent  shelves  higher  than  can  be  reached  by  the 
operator  standing  on  the  floor.  The  double  desk  should  have  a 
rail  running  lengthwise  down  the  middle  of  each  shelf,  except  pos- 
sibly the  top,  to  prevent  things  put  on  one  side  from  shoving 
things  off  on  the  other. 

Fig.  1 8  shows  a  convenient  way  of  mounting  shelves  with  iron 
pipes.  The  construction  is  evident  from  the  illustration  and  all 
parts  are  regular  stock  pipe  fitting.  It  is  sometimes  convenient  to 


24  SMALL    CHEMICAL    LABORATORIES. 

hang  shelves  from  the  ceiling  so  as  to  leave  the  whole  surface 
of  the  table  free.  If  this  is  done,  the  above  way  of  using  pipe  is 
convenient.  These  hanging  shelves  are  usually  made  quite  wide 
and  do  not  come  nearer  to  the  top  of  the  table  than  2^  to  3  feet. 
It  is  sometimes  found  more  convenient  to  bring  gas  down  from 
the  ceiling  to  the  single  or  double  tables — running  down  one  pipe 
on  each  side  of  the  reagent  shelves  and  terminating  each  in  a 
double  jet.  The  table  may,  of  course,  be  provided  with  water 
supply  and  waste  pipes  and  suction  if  thought  necessary.  The 


n 


k 

-r                                 ' 

[ 

\                  ^/7f//                                J— 

J                          L 

i                             i 

[r 

•  t           -SAe/f                     J 

\ 

J                                  [I 

] 

^ 

L       J 

Fig.   18.— Shelves   Mounted  on  Piping. 

water  may  be  brought  down  from  the  ceiling  also,  just  as  the 
gas  is. 

Reagent  Bottles. — A  neat  form  of  glass  stoppered  reagent 
bottle  for  this  table  is  that  with  flat  hood  shaped  stopper.  A  still 
better  form  is  one  devised  by  Prof.  Jewett,  of  Oberlin  College  (see 
Fig.  19),  manufactured  for  E.  H.  Sargent  &  Co.,  Chicago,  111. 
In  this  bottle,  the  mouth  and  lip  are  completely  protected  from 
dust  by  the  hood  stopper  and  its  pendant  flange,  made  in  one  piece. 
This  helps  to  keep  the  contents  of  the  bottle  pure.  These  bottles 
have  chemical  names  and  symbols  in  raised  letters  with  ground 


DESKS.  25 

surfaces,  made  in  4  and  8-oz.  sizes.  One  of  the  best  forms  of 
label  which  the  author  has  seen  is  that  which  Whitall,  Tatum  & 
Co.,  of  Philadelphia  and  New  York,  have  introduced.  This  is  a 


Fig.   19.— Jewett's  Reagent  Bottle. 

label  of  vitrified  glass  in  which  the  label  itself  presents  a  smooth 
white  glass  background,  against  which  the  transparent  letters  and 
symbols  show  distinctly.  This  label  is  more  legible  than  the  ordi- 
nary raised  letter  with  the  ground  glass  face. 


CHAPTER   V. 
TABLE  AND  APPARATUS  FOR  RAPID.  FILTRATION. 

General  Features. — Figs.  20  and  21  show  a  table  especially 
designed  for  the  use  of  long  stem  funnels.  It  is  merely  an  ordi- 
nary table,  thirty  inches  high,  provided  with  a  shelf  running  the 
entire  length  across  its  front,  eighteen  inches  below  the  top  of 


Fig.  20.— Table  for  Rapid  Filtration— Front  Elevation. 


APPARATUS    FOR    RAPID    FILTRATION.  27 

the  table.  The  shelf  is  designed  to  hold  the  beakers  which  are  to 
catch  the  filtrates.  The  funnels  pass  through  slots,  i"  x  2",  in 
the  table  top  and  are  held  in  the  arrangement  shown  in  the  illus- 
tration. This  consists  of  an  iron  rod,  screwed  fast  to  the  lower 
shelf  of  the  table  and  passing  up  through  the  top,  twelve  or  sixteen 


Fig.  21.— Table  for  Rapid  Filtration — End  Elevation. 

inches  or  even  higher.  The  funnels  themselves  are  held  in  glass 
triangles  made  of  heavy  glass  rod,  J4"  in  diameter,  which  in 
turn  are  clamped  to  the  rods,  at  any  height  desired,  by  means  of 
right-angled  clamps.  These  filter  stands  are  very  neat  and  are 
cleaner  than  the  wooden  ones.  A  piece  of  rubber  tube  should  go 


28  SMALL    CHEMICAL    LABORATORIES. 

around  the  glass  triangle  where  it  is  gripped  by  the  clamp.  The 
funnel  stems  should  be  bent  in  a  loop  so  as  to  keep  them  always 
full  of  liquid.  Instead  of  making  the  bend,  the  tube  may  be 
merely  drawn  out  slightly,  reducing  the  diameter  to  about  1-16 
inch.  In  order  to  have  them  fill  rapidly  it  is  essential  that  the 
filter  paper  be  put  in  tight,  so  that  no  air  can  leak  past.  In  con- 
nection with  this  table,  the  writer  has  used  to  advantage  the  de- 
vice for  washing  precipitates  shown  in  the  cut.  It  consists  merely 
of  a  bottle  standing  on  a  shelf,  either  fastened  to  the  wall  or  sup- 
ported from  the  table,  provided  with  a  siphon  tube  to  which  is 
attached  a  long  flexible  rubber  tube  terminating  in  a  jet  and 
closed  by  Mohr's  pinch-cock.  This  apparatus  will  be  found  very 
useful  for  washing  such  precipitates  as  magnesium  pyrophos- 
phate,  phospho-molybdate,  etc.  The  small  cupboard  at  the  back 
of  the  table  is  for  filter  papers.  It  may  be  dispensed  with  en- 
tirely and  the. japanned  tin  filter  cases,  sold  by  dealers  in  chemical 
apparatus,  substituted.  These  latter  hold  five  sizes  of  filter 
papers,  ranging  from  19  cm.  down. 

Wash  Bottles. — For  covering  the  necks  of  wash  bottles  to 
be  used  for  hot  water,  sheet  cork  will  be  found  the  neatest  ma- 
terial. It  is  a  good  non-conductor  of  heat  and  does  not  flake 
off  on  the  hands  as  does  asbestos.  It  is  usually  sold  in  plates 
8x4  inches  and  J/6  inch  thick.  A  piece  of  this  is  cut  so  as  to  cover 
the  neck  of  the  flask  with  about  an  inch  lap.  One  end  of  this 
piece  is  then  shaved  with  a  sharp  knife  until  it  tapers  to  a  thin 
edge,  and  the  cork  is  placed  in  hot  water  to  soak.  It  is  then 
partly  dried  on  a  towel,  and  curled  around  the  neck  of  the  flask. 
Mucilage  or  glue  is  used  to  hold  the  two  ends  of  the  cork  to- 
gether, string  being  wrapped  around  until  this  dries,  which  can 
be  hastened  by  boiling  water  in  the  flask. 

Asbestos  paper  is  much  used  for  this  purpose  also.  The 
author's  objection  to  it  has  always  been,  that  it  flakes  off  on  the 
hand  and  these  flakes  are  liable  to  get  into  the  filter  paper  or  solu- 
tion. Where  asbestos  is  used,  therefore,  it  is  safest  to  cover  this 
with  cloth.  The  asbestos  is  wet  and  wrapped  around  the  neck  of 
the  flask  and  partially  dried.  A  strip  of  flannel  or  felt  is  then 
pasted  around  this  so  as  to  entirely  cover  the  asbestos. 


CHAPTER   VI. 
IGNITION  TABLE  AND  APPARATUS  FOR  IGNITIONS. 

General  Features. — In  the  scheme  which  we  outlined  in  the 
opening  paragraph  of  this  book,  of  having  a  place  for  every- 
thing, it  was  stated  that  there  should  be  a  separate  table  for  ig- 
nitions. The  size  of  this  table  will,  of  course,  depend  on  the 
number  of  ignitions  which  are  to  be  made  at  one  time.  Ten  or 
twelve  can  easily  be  carried  out  at  the  same  time  on  a  table  with 
a  top  3x4  feet.  There  is  nothing  particularly  different  about  the 
ignition  table  from  any  other  table  in  the  laboratory.  It  should, 
of  course,  have  a  concrete,  stone,  slate  or  lead  top  and  can  be 
made  similar  to  the  hood  table  described  in  Chapter  II. 
Nothing  is  gained  by  having  a  very  wide  table.  If  in  the  middle  of 
the  room,  a  table  three  feet  wide  is  of  ample  width,  while  two 
feet  will  do  for  one  set  against  the  wall.  The  gas  tubes  should 
be  frequent  and  there  should  be  some  mechanical  means  for  sup- 
plying air  to  the  blast  lamps.  Double  gas  jets  every  foot  will 
allow  an  ignition  every  six  inches.  The  gas  pipes  should  be  run 
around  in  front  just  below  the  top,  as  in  the  hood  table. 

Crucible  Supports. — Tripods  may  be  used  for  holding  the 
crucibles ;  or  ring  supports,  sold  by  all  dealers,  can  be  used. 
These  latter  are  to  be  preferred,  as  the  height  of  the  crucible 
above  the  flame  can  be  regulated.  They  cost,  however,  about 
four  or  five  times  as  much  as  the  tripods.  In  getting  supports, 
those  with  triangular  bases  take  up  a  little  less  room  than  the 
other  kind.  If  a  concrete  top  is  to  be  used,  the  cheapest  and 
best  way  of  supporting  the  crucibles  is  by  iron  rods  projecting 
from  the  concrete  top,  from  six  to  seven  inches  apart  and  ten  to 
twelve  inches  from  the  edge  of  the  table.  Each  rod  should  pro- 
ject fourteen  inches  above  the  table  top.  To  do  this,  cut  the  rods 
of  the  proper  height  and  insert  in  an  upright  position  in  the 
rough  wood  top  of  the  table  before  the  concrete  is  poured  on. 
This  latter  will  of  course  run  around  them  and  hold  them  very 
firmly  in  position.  The  crucibles  are  then  held  at  any  height 
desired  by  means  of  ring  clamps  such  as  are  used  with  supports. 


SMALL    CHEMICAL    LABORATORIES. 


The  best  triangle  to  use  with  the  crucible  is  one  of  platinum. 
Its  first  cost  is  of  course  high,  but  they  will  stand,  if  carefully 
used,  any  amount  of  wear.  The  platinum  triangle  for  a  15  CC. 
crucible  weighs  about  8  grams  and  one  for  a  30  CC.  crucible  will 
weigh  about  12  grams.  Special  clamp  supports,  for  platinum  tri- 
angles are  made.  These  hold  the  triangle  firmly  in  place  and 
prevent  the  wire  from  bending  down.  They  also  require  much 
less  platinum  wire  than  the  ordinary  form,  three  to  five  grams 
being  sufficient  for  ordinary  crucibles.  Nothing  is  gained  by 
buying  platinum  wire  and  bending  triangles  from  this.  The  best 


3"- 


Fig.   22.— Water  Blower  Fig.  23.— Details  of  the  Aspirator 

for  Blast  Lamp.  for  Water  Blower. 

of  the  pipe  stem  triangles  are  those  made  of  iron  covered  with 
flanged  pipe  stems. 

Blast  Lamp. — Every  laboratory  should  have  a  blast  lamp, 
since  its  use  saves  much  time  and  simplifies  many  operations  of 
the  laboratory,  and  indeed  certain  determinations  (such  as  silica) 
cannot  be  performed  correctly  without  one.  They  can  be  ob- 
tained in  many  forms.  Bunsen's  is  one  of  the  oldest  and  best 
of  these,  and  it  is  illustrated  in  all  catalogues  of  chemical  appara- 
tus. It  is  so  fixed  that  the  direction  of  the  flame  can  be  altered 
by  turning  a  thumbscrew.  Another  good  blast  lamp  is  Weis- 


APPARATUS  FOR  IGNITIONS.  31 

negg's,  which  is  mounted  on  ball  joints.  It  can  be  turned  about 
a  greater  range  than  Bunsen's,  but  is  also  more  expensive.  The 
upright  blasts  cost  about  as  much  as  the  adjustable  ones  and 
are  not  so  useful.  It  is  generally  better  to  play  the  flame  at 
an  angle  upon  the  bottom  of  the  crucible  than  directly  upon  it, 
for  in  the  former  method  the  products  of  combustion  are  swept 
away  from  the  crucible,  while  in  the  latter  they  are  carried  up  and 
around  it,  entirely  surrounding  the  crucible  and  cutting  off  the 
supply  of  oxygen  from  the  latter,  possibly  causing  a  reduction, 
etc.,  of  the  precipitate  being  ignited.  For  this  reason  the  adjust- 
able blast  lamps  are  better  than  the  upright  ones.  Crucibles  to 
be  ignited  over  the  blast  lamps  should  be  placed  with  their  bot- 
toms projecting  through  a  round  hole  in  a  piece  of  platinum  foil, 
which  in  turn  rests  upon  a  piece  of  asbestos  board  with  a  slightly 
larger  hole  cut  into  it.  While  this  method  of  supporting  a 
crucible  is  not  essential  and  indeed  is  not  the  one  generally  used, 
it  will  probably  give  better  results  in  all  cases  where  a  precipi- 
tate is  to  be  ignited  to  a  constant  weight  or  when  reduction  by 
or  absorption  of  the  products  of  combustion  by  the  precipitate 
is  likely  to  occur. 

Air  Blast. — For  supplying  air  to  blast  lamps,  every  chemist 
is  familiar  with  the  foot  bellows.  No  manufacturing  concern, 
however,  can  afford  to  use  their  chemist's  time  for  pumping  a 
foot  blower,  so  it  is  more  economical  to  arrange  to  have  some 
mechanical  means  of  doing  this  work.  If  high  pressure  air 
is  used  around  the  plant,  it  may  be  run  into  the  laboratory  for 
this  purpose.  In  blast  furnaces,  the  air  from  the  blowing  engine ; 
in  machine  shops,  air  for  the  supply  of  pneumatic  tools,  etc.,  is 
usually  at  hand.  If  the  pressure  is  high,  reducing  valves  should 
be  put  in  between  the  laboratory  and  the  compressor  or  blowing 
engine. 

The  writer  has  in  his  laboratory  a  blower  which  gives  ex- 
cellent service  and  is  working  under  a  water  pressure  of  about 
60  Ibs.  While  there  is  nothing  new  about  it,  still  it  may  be  worth 
describing  here. 

Its  construction  is  shown  in  Fig.  22.  Referring  to  this 
illustration,  A  is  the  aspirator  whose  detail  construction  is  shown 
in  Fig.  23.  ] ' ,  Fig.  23,  is  an  ordinary  half-inch  T.  K  is  a  piece 
of  half-inch  pipe  connected  with  the  valve  H.  Into  the  tube, 
K,  is  screwed  a  small  tap  through  the  middle  of  which  has  been 


32  SMALL    CHEMICAL    LABORATORIES. 

bored  a  1-16  inch  hole.  L  is  another  piece  of  half-inch  pipe 
leading  to  the  drum,  B.  The  third  opening  of  the  T  can  be  con- 
nected with  the  line  for  aspirating  as  shown.  The  drum  B,  Fig. 
22,  consists  of  a  three-inch  pipe,  22  inches  long  and  capped  at 
both  ends.  C,  G}  and  E  are  all  made  of  half-inch  pipe.  G  leads 
to  the  waste.  The  air  for  the  blast  lamps  is  drawn  off  at  D. 
This  apparatus  will  easily  give  sufficient  air  for  two  blast  lamps. 
It  can '  be  purchased,  if  desired,  in  a  little  neater  form,  from 
several  dealers  in  chemists'  supplies.  A  small  drum  may  be 
placed  after  the  blower  to  catch  any  water  splashed  into  the  air 
line.  One  may  be  made  by  capping  a  piece  of  3-inch  pipe,  12  or 
14  inches  long,  at  both  ends.  It  should  stand  upright  and  the  air 
should  enter  and  leave  at  the  upper  end,  and  there  should  be  a 
small  tap  at  the  bottom  for  drawing  off  any  water  that  may  col- 
lect in  the  pipe.  The  water  blower  in  use  by  the  writer,  however, 
seems  to  give  air  free  from  water  and  no  trap  would  be  needed 
with  it. 

In  place  of  the  water  blower  described,  a  small  automatic 
air  pump  such  as  is  used  for  forcing  beer  from  the  cellar  into 
the  bar,  and  by  physicians  and  barbers,  may  be  used.  It  should 
be  of  the  piston  variety,  double  acting  and  automatic.  A  large 
receiver  or  drum  should  follow  this  to  equalize  the  pressure.  A 
small  Root  blower  or  a  Crowell  blower  run  from  a  shaft  or  by  a 
motor  may  be  used,  but  either  is  somewhat  noisy  if  placed  in  the 
laboratory  and  like  all  machines  needs  repair  and  attention. 

Dr.  Porter  W.  Shimer  described  in  the  Chemical  Engineer 
for  April,  1905,  an  apparatus  for  producing  either  blast  or  suc- 
tion. It  consists  of  a  No.  16,  "Goulds  Air-Pressure  or  Vacuum 
Pump"  (manufactured  by  The  Goulds  Manufacturing  Co.,  Sen- 
eca Falls,  New  York).  It  is  a  hand  pump,  operated  by  a  wooden 
lever  about  five  feet  in  length,  and,  by  proper  arrangement  of 
valves,  it  can  be  used  either  to  compress  air  or  to  create  vacuum. 
The  diameter  of  cylinder  is  6  inches  and  the  stroke  is  10  inches. 
The  displacement  of  free  air  per  stroke  is  280  cubic  inches.  The 
inlet  and  outlet  are  1%-inch  pipes. 

The  pump  is  connected  with  two  boilers  such  as  are  used 
for  hot  water  in  connection  with  kitchen  ranges.  These  boilers 
need  not  be  new,  for  rejected  ones  may  be  made,  with  a  little 
repairing,  as  good  as  new  ones  for  this  purpose.  The  cylinder  for 


APPARATUS  FOR  IGNITIONS.  33 

blast  in  Dr.  Shimer's  laboratory  is  6  feet  high  and  18  inches  in 
diameter.  The  one  for  suction  is  5  feet  high  and  14  inches  in 
diameter.  The  manner  of  making  the  connections  and  the  position 
of  the  valves  are  shown  in  Fig.  24. 

By  a  proper  arrangement  of  the  valves  the  pump  may  be  set 
for  vacuum  and  the  air  may  be  exhausted  from  the  other  cylinder 
for  purposes  of  filtration.  By  this  means  any  degree  of  vacuum 
desired  for  hastening  filtration  may  be  obtained.  This  cylinder 
and  the  piping  should  be  coated  inside  with  acid-proof  asphaltum 
paint  to  protect  it  from  the  corrosive  action  of  acid  fumes  drawn 
in  during  filtration  of  strong  acid  solutions.  This  may  also  be 
guarded  against  by  sucking  the  air  through  two  bottles  partially 
filled  with  water  containing  a  little  caustic  soda.  The  entrance 
tube  to  each  bottle  should  pass  below  the  surface  of  the  liquid. 

Both  blast  and  suction  cylinders  may  be  connected  with 
piping  containing  as  many  valved  outlets  as  may  be  desired. 

Ignitions  in  a  Muffle  Furnace. — Small  muffle  furnaces,  such 
as  are  used  in  assaying  gold  and  silver  ores,  are  often  used  in  large 
laboratories.  When  many  ignitions  are  to  be  made  they  undoubt- 
edly have  some  points  in  their  favor.  In  most  small  laboratories, 
however,  they  are  uneconomical,  as  the  gas  or  gasoline  required 
to  heat  them  up  is  considerably  more  than  that  which  would  be 
required  to  ignite  a  dozen  or  so  precipitates  over  Bunsen  burners 
and  blast  lamps.  If  heated  by  coal  they  are  a  nuisance  and  a 
source  of  dirt.  When  fire  assays  are  also  made  the  muffle  is  of 
course  convenient  for  ignitions.  They  are  described  in  Chapter 
XIII. 

Platinum  Crucibles. — These  should  be  made  of  the  best  ham- 
mered ware  free  from  alloy.  They  usually  weigh  as  much,  lids 
included,  in  grams  as  they  hold  in  cubic  centimeters — that  is  a 
15  c.  c.  crucible  with  lid  should  weigh  about  15  grams.  For  ordi- 
nary ignitions  a  15  c.  c.  crucible  will  be  large  enough,  and,  indeed, 
where  9  cm.  filters  are  used  and  small  precipitates  are  collected, 
even  10  c.  c.  crucibles  will  answer  satisfactorily.  For  fusions,  a 
30  c.  c.  crucible  will  be  found  sufficient.  For  ignitions  it  is  a 
good  plan  to  have  all  of  the  crucibles  weigh  approximately  be- 
tween 15  and  1 6  grams,  as  by  this  means,  considerable  time  is 
saved  in  weighing  a  lot  of  them,  one  after  the  other,  because  the 
large  weights  on  the  balance  pan  do  not  have  to  be  changed. 

The  crucibles  may  be  numbered  with  a  small  steel  die,  or,  if 


34 


SMALL    CHEMICAL    LABORATORIES. 


Fig.  24.— Pump  and  Receivers  for  Blast  or  Suction. 


APPARATUS  FOR  IGNITIONS.  35 

there  are  only  a  few,  this  may  be  done  with  dots;  thus,  V,  \  \t 
etc.  A  wooden  mould  and  plug  should  be  provided  and  the 
crucibles  kept  free  from  dents  and  distortion  by  shaping  them  up 
in  this.  If  a  mould  can  not  be  obtained,  a  recess  casting  of  the 
crucible  in  plaster  or  cement  may  easily  be  made,  when  it  is  new, 
and  the  end  of  a  broomstick  rounded  off  for  a  plug  to  fit  inside. 

Porcelain  Crucibles. — Platinum  crucibles  can  not  be  used  for 
the  free  metals,  the  easily  reduced  metallic  oxides  and  the  salts 
of  the  heavy  metals,  such  as  lead,  tin,  bismuth,  etc.,  and  for  ignit- 
ing such  precipitates  porcelain  crucibles  must  be  resorted  to. 
When  platinum  can  be  used,  little  except  first  cost  is  saved  by 
employing  porcelain  crucibles,  as  the  breakage,  etc.,  of  these  lat- 
ter is  greater  than  the  wear  and  tear  and  interest  on  the  former. 
Porcelain  crucibles  may  be  obtained  in  sizes  ranging  from  a  few 
cubic  centimeters'  capacity  up  to  that  of  several  hundred  c.  c. 
They  are  made  of  both  Royal  Berlin  and  Royal  Meissen  proce- 
lain,  the  former  being  the  best  and  costing  considerably  more 
than  the  latter.  The  Royal  Berlin  porcelain  crucibles  are  of  a 
more  squat  form  than  those  of  the  other  makes. 

The  crucibles  may  be  obtained  with  vitrified  consecutive  num- 
bers or  letters  on  the  side,  by  which  to  distinguish  them,  at  a 
slightly  higher  price  than  the  unmarked;  or  they  may  be  num- 
bered with  a  lead  pencil  under  the  unglazed  bottom,  before  ignit- 
ing and  weighing,  the  ash  of  the  lead  burning  into  the  crucible 
and  making  a  permanent  mark. 

Porcelain  Gooch  crucibles  may  also  be  purchased  and  these 
are  handy  for  some  precipitates.  Those  with  the  movable  bottom 
may  be  used  to  advantage  to  collect  the  carbon  for  combustion  in 
steel  analysis.  When  precipitates  have  to  be  heated  in  an  atmos- 
phere of  hydrogen  sulphide,  hydrogen,  etc.,  Rose's  form  of 
crucible  may  be  used.  This  consists  of  a  porcelain  crucible  with 
a  perforated  cover  through  the  hole  of  which  a  porcelain  tube 
passes.  When  this  form  of  crucible  is  not  at  hand  an  ordinary 
crucible  may  be  made  to  serve,  being  covered  by  inverting  over  it 
an  ordinary  clay  pipe,  the  gas  being  led  in  through  the  stem  of  the 
latter. 

Crucible  Tongs. — These  are  made  in  a  number  of  patterns 
and  of  a  number  of  metals.  For  ordinary  ignitions,  in  a  platinum 
crucible,  over  a  burner,  the  so-called  double  bent  tongs  will  be 
found  most  useful.  They  allow  the  removal  of  the  lid  from  the 


36  SMALL    CHEMICAL    LABORATORIES. 

crucible  and  the  tilting  of  the  latter  on  the  triangle.  For  remov- 
ing crucibles  from  a  muffle  furnace,  Julian's  crucible  tongs  may 
be  used.  Blair  also  has  devised  a  special  form  of  tongs,  scissors 
shaped,  in  which  the  curved  and  bent  part  of  the  tongs  is  of  plati- 
num. 

A  good  pair  of  tongs  is  one  made  of  solid  nickel  or  German 
silver  and  having  platinum  shoes  on  the  ends.  The  shoes  are  to 
be  preferred  to  the  tips  riveted  on.  The  tongs  may  be  obtained 
single  or  double  bent,  the  former  being  the  most  convenient.  In 
transferring  a  crucible  from  the  triangle  to  the  desiccator  with 
these  tongs,  the  lid  is  slipped  to  one  side,  just  far  enough  to 
allow  the  edge  of  the  crucible  to  be  gripped  by  the  point  of  the 
tongs.  Where  a  cheaper  pair  of  tongs  is  desired,  steel  forged, 
nickel-plated  tongs  are  the  best. 

Miscellaneous. — Desiccators,  in  which  to  cool  crucibles  before 
weighing,  are  of  a  number  of  forms,  Scheibler's  is  perhaps  the 
best.  This  may  be  obtained  in  a  number  of  sizes,  of  which  the  6-inch 
is  probably  most  suited  to  laboratory  purposes,  as  it  can  be  carried 
back  and  forth  from  the  ignition  table  to  the  balance  room.  For 
holding  the  crucibles  in  the  desiccators,  porcelain  or  aluminum 
plates  can  be  purchased.  The  latter  cool  the  crucible  quicker  as 
the  metal  carries  off  the  heat  faster.  Large  desiccators  may  be 
had  and,  when  these  are  to  be  left  in  the  balance  room,  are  found 
useful.  The  porcelain  plates  which  come  with  large  desiccators 
are  usually  perforated  with  holes  entirely  too  small  for  crucibles. 
If  the  dealer  is  furnished  a  rough  drawing,  showing  size  and 
number  of  holes  desired,  he  will  usually  make  an  aluminum  plate 
at  small  additional  cost.  Calcium  chloride  is  used  as  the  moisture 
absorber  in  all  portable  desiccators. 

It  is  often  more  convenient  to  lay  precipitates  aside  as  they 
are  filtered  and  ignite  later  on;  an  8-inch  bell  glass  of  the  low 
form  resting  on  a  glass  plate  will  be  found  convenient  for  keep- 
ing these  out  of  the  dust.  The  paper  may  be  marked,  either 
before  being  placed  in  the  funnel  or  when  taken  out,  with  a  soft 
lead  pencil.  If  an  acid  dish  or  basin  containing  a  little  strong 
sulphuric  acid  is  placed  under  the  bell  jar,  and  the  precipitates 
are  placed  in  a  watch  glass  resting  on  the  acid  dish,  the  acid  will 
dry  the  precipitates  and  filter  papers,  provided  they  are  left  in 
long  enough. 


CHAPTER   VII. 
TABLE  AND   APPARATUS    FOR   TITRATIONS. 

Burette  Stand. — A  neat  burette  table  is  shown  in  Fig.  25.  It 
is  32  inches  high,  4  feet  long,  and  2^  feet  wide.  It  has  a  shallow 
cupboard  below  and  a  narrow  drawer.  The  bottom  of  the  drawer 
extends  only  half  way  across  the  table,  so  that  it  does  not  interfere 
with  the  tubes  leading  from  the  burettes  to  the  bottles.  The 


Fig  25.— Burette  Table. 


38, 


SMALL    CHEMICAL    LABORATORIES. 


burette  holder  illustrated  is  merely  a  wooden  frame.  It  is  of  the 
form  shown,  having  holes  bored  through  where  the  burettes  are  to 
go.  The  burettes  themselves  are  held  in  place  by  a  wedge,  as 
illustrated  in  Fig.  26.  In  place  of  the  frame  shown,  iron  rods 
may  be  passed  through  holes  in  the  table  and  fastened  to  the 
upper  framework  of  the  cupboard.  The  burette  is  then  held  in 
place  by  the  ordinary  burette  clamps,  over  the  jaws  of  which 
should  be  slipped  a  piece  of  rubber  tubing  to  give  them  a  firm 
grip.  Or,  since  this  tubing  is  apt  to  rot  and  stick  to  the 
burette,  a  piece  of  felt  may  be  glued  inside  the  jaws  for  this 
burette.  Since  burettes  are  always  held  in  an  upright  position, 
the  clamps  with  strong  springs  to  close  the  jaws  are  more  con- 


Fig.  26.— Method  of  Holding  Burette  in  the  Frame. 

venient  than  the  adjustable  ones  closed  by  a  thumbscrew^  since  it 
is  easier  to  get  the  burettes  in  and  out  for  cleaning,  etc.  On  the 
other  hand,  they  do  not  last  as  long  because  the  springs  break. 

Burettes, — The  most  convenient  burette  is  the  one  having  a 
three  way  stop  cock  and  side  tube  for  filling.  In  the  table  shown, 
the  standard  solutions  are  forced  up  into  the  burettes  from  the 
bottles  in  the  cupboard  below,  by  use  of  an  atomizer  bulb.  In 
using,  enough  solution  should  be  forced  into  the  burette  to  fill  it 
above  the  zero  point.  The  excess  is  then  run  back  into  the  bot- 
tle below.  The  bottle  holding  the  solution  should  be  provided 
with  a  three  hole  rubber  stopper.  Through  one  of  these  stoppers 
the  tube  leading  to  the  burette  passes.  This  tube  should,  of 
CG-uirse,  reach  nearly  to  the  bottom  of  the  bottle.  The  second  and 


APPARATUS  FOR  TITRATIONS. 


39 


third  holes  are  provided  with  short  pieces  of  tubing  reaching  just 
inside  the  bottle.  One  of  these  tubes  is  attached  to  the  atomizer 
bulb  and  the  other  to  a  piece  of  rubber  tubing  passing  through  a 
hole  in  the  table  top  and  extending  about  three  or  four  inches 
above  the  latter.  Instead  of  a  three-hole  rubber  stopper,  a  two- 
hole  one  may  be  used  and  a  Y-tube  inserted  in  one  of  the  holes. 
The  atomizer  bulb  is  then  to  be  attached  to  one  of  the  branches 
of  the  "Y"  and  the  rubber  tube  to  the  other. 

In  forcing  the  solution  up,  the  stop  cock  of  the  burette  is 
turned  to  make  connection  with  the  bottle,  the  rubber  tubing  is 
pinched  with  the  left  hand  and  the  atomizer  bulb  is  worked  with 
the  right.  When  the  solution  reaches  a  certain  point  in  the 
burette,  determined  by  practice  (usually  the  25  or  30  c.  c.  mark), 
the  pressure  in  the  bottle  is  sufficient  to  fill  the  burette.  At  this 
point,  the  right  band  is  withdrawn  from  the  atomizer  bulb  and 
placed  on  the  stop  cock.  As  soon  as  the  solution  passes  the  zero 
point,  the  connection  between  the  bottle  and  the  burette  is  cut  off 
by  the  stop  cock.  All  this  time  the  rubber  tube  has  been  kept 
tightly  closed  by  pinching  between  the  thumb  and  forefinger  of 
the  left  hand.  This  is  now  released  and  the  pressure  in  the  bot- 
tle relieved.  The  excess  of  solution  in  the  burette  can  then  be 
run  back  into  the  bottle.  This  same  form  of  burette  can  also  be 
obtained  in  a  very  convenient  form,  with  an  automatic  zero  point 
and  an  overflow  reservoir  similar  to  that  of  the  pipette  illustrated 
in  Fig.  29,  from  Eimer  &  Amend,  i8th  St.  and  3d  Ave.,  New 
York.  These  latter  are  very  useful,  as  they  require  no  adjusting 
to  the  zero  point  when  filling  and  consequently  save  time. 

Instead  of  forcing  the  solution  up  from  a  bottle  in  a  cup- 
board below,  if  permanganate,  bichromate,  iodine,  and  other  solu- 
tions attacking  rubber  tubing  or  decomposed  by  the  light  are 
not  used,  a  shelf  may  be  placed  on  the  wall  back  of  the  table  and 
the  solutions  run  down  into  the  bottle.  If,  however,  standard 
solutions  attacking  rubber  are  used,  the  cupboard  below  the  table 
is  the  thing,  since  in  the  shelf  arrangement  the  solution  is  in  con- 
tact with  the  rubber  tube  used  to  join  the  burette  tube  below  to 
the  tube  leading  from  the  bottle;  hence  it  soon  eats  a  hole  in  the 
latter.  If  this  happens  at  night,  the  whole  bottle  of  standard 
solution  will  probably  leak  out,  and  an  eight-liter  bottle  of  per- 
manganate would  make  a  mess,  in  any  event;  while,  if  the  labora- 
tory was  located  on  the  second  floor,  it  would  probably  damage 


40  SMALL    CHEMICAL    LABORATORIES. 

the  ceiling  of  the  room  below.  Where  the  solutions  do  not  attack 
rubber  it  is,  of  course,  more  convenient  to  have  the  bottles  on  a 
shelf  and  run  solutions  down  into  the  burettes  by  a  siphon  tube. 
The  shelf,  however,  must  be  placed  above  the  zero  point  of  the 
burettes,  in  order  to  bring  the  solutions  to  the  zero  point  when 
the  bottles  are  nearly  empty.  When  standard  solutions  are  de- 
composed by  light,  they  may  be  kept  in  bottles  painted  black  with 
asphalt  paint,  or  the  bottles  may  be  provided  with  a  hood  or  bag 
cover,  of  heavy  black  cloth.  When  standard  alkali  and  other 
solutions  attacking  glass  are  used,  the  burette  should  be  of  the 
old  style  Mohr's  form,  with  rubber  connections  and  attachments 
for  rilling  from  the  side. 

Automatic  Zero  Burette. — The  ordinary  form  of  burette  may 


Fig.  27. — Burette  with  Automatic  Zero  Point  Filler. 

be  made  to  answer  as  a  zero  point  burette  by  the  arrangement 
shown  in  Fig.  27.  This  consists  in  placing  the  top  of  the  bottle 
holding  the  standard  solution  below  the  zero  point  of  the  burette. 
The  tube  leading  from  the  former  to  the  latter  is  then  run  down 
into  the  burette,  level  with,  or  a  little  above  the  zero  point.  This 
arrangement  will  siphon  off  the  excess  of  solution  in  the  burette, 
to  the  zero  point,  after  a  few  adjustments  and  trials  of  the  tube 
in  different  positions.  The  writer  has  at  times  experienced  more 
or  less  trouble  with  this  form  of  burette  from  the  drop  which 
collects  on  the  end  of  the  tube  falling  into  the  burette.  This  may 
be  obviated  by  having  the  siphon  tube  drain  into  the  bottle  as 
much  as  possible  and  to  this  end  it  should  be  bent  as  shown  in  the 


APPARATUS  FOR  TITRATIONS.  41 

cut.  The  end  leading  into  the  burette  should  also  be  drawn  very 
slightly  towards  a  point.  This  latter  will  hold  the  drop.  It  is 
usually  hard  to  get  a  rubber  stopper  small  enough  to  go  into  the 
tube  and  with  a  large  enough  hole  to  admit  the  tubing,  so  as  all 
that  is  needed  is  something  to  hold  the  tube  in  position  an  ordi- 
nary cork  can  be  used.  A  few  V-shaped  grooves  should  be  cut 
lengthwise  down  its  sides  to  admit  air  in  and  out  of  the  burette. 

Appliances  to  Aid  in  Reading  the  Burette. — For  aiding  the 
operator  in  reading  the  burette,  various  appliances  have  been 
suggested.  For  colored  solutions  such  as  permanganate,  nothing 
is  needed,  but  for  colorless  ones  floats  are  sometimes  used.  A 
new  burette,  designed  by  Schellbach,  has  recently  been  placed  on 
the  market  and  may  be  obtained  from  a  number  of  dealers  in 
chemical  apparatus.  This  burette  has  a  blue  enameled  line,  with 
a  white  enameled  background,  running  lengthwise  down  the  bur- 
ette. At  the  level  of  the  solution,  this  line  presents  the  appearance 
of  an  X  and  the  level  is  taken  as  the  point  where  the  two  V's 
come  together. 

Burettes  having  a  white  enameled  background  for  use  with 
colored  solutions  can  also  be  obtained.  A  card  having  a  piece  of 
black  paper  pasted  across  its  lower  half,  or  having  this  part 
blackened,  will  aid  in  reading  colorless  solutions  in  an  ordinary 
clear  glass  burette.  If  held  with  the  line  of  division  between  the 
black  and  white,  about  an  eighth  of  an  inch  below  the  surface 
of  the  liquid,  and  the  eye  brought  on  a  level  with  it,  the  meniscus 
can  then  be  seen  by  transmitted  light,  bounded  below  by  a  sharply 
defined  black  line. 

Caps  for  Burettes. — If  the  top  of  the  burette  is  open  it  should 
be  closed  by  a  small  glass  cap,  slipping  loosely  over  it.  One  can 
be  easily  made  from  a  test  tube,  as  follows:  Select  a  tube  which 
slides  over  the  burette  top  and  mark  it  about  one  and  a  half  inches 
from  the  closed  end  with  a  sharp  file.  Wrap  two  strips  of  wet 
filter  paper  around  the  tube,  one  a  little  above  and  one  a  little 
below  the  mark  and  about  one-eighth  inch  apart.  Direct  the 
point  of  a  small  blowpipe  flame  against  this  opening  between  the 
two  strips  and  revolve  the  tube.  A  crack  will  start  and  follow 
the  flame  around  the  tube.  This  is  a  simple  way  of  cutting  glass 
cylinders  or  tubes,  and  a.  five-pound  bottle  may  be  turned  into 
a  waste  jar  for  the  burette  table  in  the  same  way ;  scratching  it, 
wrapping  wet  newspaper  around  it,  and  cracking  it  with  a  flame. 


42  SMALL    CHEMICAL    LABORATORIES. 

The  writer  has  found  this  way  much  more  satisfactory  than  the 
methods  usually  recommended  for  the  purpose. 

Portable  Burettes  and  Solutions. — Burettes  mounted  on  the 
bottles  containing  the  solutions  with  which  they  are  to  be  filled 
are  sometimes  used  and  will  be  found  useful  when  only  a  few 
titrations  are  to  be  made  and  these  few  not  very  often.  They 
are  usually  fitted  with  automatic  zero  point.  The  forms  designed 
by  Squibb  and  Knopler  are  described  in  almost  every  catalogue 
of  chemical  apparatus.  The  great  disadvantage  of  these  arrange- 
ments is  the  small  size  of  the  bottles,  which  is  usually  two  liters 


Fig.  28.— Burette  and  Solution  on  Movable  Stand. 

capacity,  and  of  the  burette,  which  is  never  larger  than  50  c.  c. 
If  made  larger  the  bottle  is  too  heavy  to  move  about,  and  the 
burette  too  long. 

When  space  is  limited,  a  burette  and  bottle  mounted  on  a 
stand  provided  with  rollers  will  prove  handy,  as  it  can  be  pushed 
back  out  of  the  way  when  not  needed.  Fig.  28  shows  such  an 
apparatus.  Its  construction  is  evident  from  the  illustration.  It 
consists  of  a  stand,  mounted  on  rollers,  to  the  front  of  which  is 
fastened  an  iron  rod,  two  feet  long  and  Y^  or  5-16  inch  in  diame- 
ter. The  lower  end  of  the  rod  is  flattened  and  through  the  flat- 


APPARATUS  FOR  TITRATIONS. 


43 


tened  end  are  bored  two  small  holes.  Screws  through  these  holes 
fasten  the  rod  to  the  stand.  The  burette  is  then  clamped  to  the 
rod  with  jaw  clamps  and  the  solution  is  forced  up  either  by  a 
bulb  or  suction.  The  tube  leading  from  the  bottle  to  the  burette 
is  fixed  to  siphon  off  the  excess  to  zero  as  described  previously. 
The  bottle  should  be  kept  in  place  on  the  stand  by  three  small 
blocks  nailed  on  top  of  the  latter  close  to  the  bottle ;  for,  if  the 
bottle  slides  around,  it  will  break  the  tube  leading  to  the  burette. 
Of  course,  any  form  of  burette,  either  with  or  without  automatic 
zero  point,  may  be  attached  to  the  stand,  and  if  the  permanganate, 
bichromate,  etc.,  are  to  be  used  with  the  apparatus,  the  bottle 
should  be  painted  black,  etc. 

Pipettes. — For  rapidly  delivering  known  volumes  of  solutions 
the  automatic  pipette,  shown  in  Fig.  29,  will  be  found  very  use- 
ful. The  bottle  acting  as  a  reservoir  should  be  placed  upon  a 
shelf  and  the  solution  run  down  into  the  pipette.  Since  these 
pipettes  are  light  compared  with  burettes,  they  can  be  joined 
directly  on  to  the  siphon  tube  leading  from  the  reservoir  by 
fusion  and  used  for  solutions,  such  as  ammonium  molybdate  in 
nitric  acid,  which  attack  rubber  rapidly.  The  siphon  tube  should 
be  made  of  heavy  walled  glass  tubing  so  as  to  resist  breakage. 
The  pipette  may  be  fastened  to  a  stand  and  the  stand  may  be 
mounted  on  rollers,  or  not.  Or  the  pipette  may  be  mounted  on 
the  frame  of  the  burette  table.  Before  fastening  the  pipette  to 
the  stand  or  frame,  the  bottle  should  be  placed  on  the  shelf  and 
moved  about  until  the  pipette  is  against  its  support.  The  pipette 
may  then  be  fastened  to  the  support  by  wire  or  a  narrow  thin 
brass  band  or  spring. 

Caustic  soda  and  other  solutions  which  absorb  carbon  dioxide 
should  be  protected  from  the  air,  or  the  air  entering-  the  bottle 
should  be  freed  from  the  carbon  dioxide  by  passing  it  over  an 
absorbent.  One  of  the  simplest  methods  is  to  place  a  layer  of 
kerosene  on  top  of  the  solution,  effectually  protecting  it  from  the 
air.  Another  method  is  to  pass  the  air  through  a  tube  containing 
soda  lime,  which  absorbs  carbon  dioxide.  The  soda  lime  tube 
may  be  stuck  through  one  hole  of  a  doubly  perforated  stopper, 
the  siphon  tube  passing  through  the  other. 

Occasionally  burettes  will  not  run  clean  and  small  drops  will 
adhere  to  their  sides  causing  the  readings  to  be  too  low.  To 
remedy  this,  allow  a  weak  solution  of  chromic  acid  to  stand  in  the 


44 


SMALL    CHEMICAL    LABORATORIES. 


burette  for  several  hours.  To  prepare  this  solution,  add  about  25 
grams  of  potassium  bichromate  to  150  c.  c.  of  water  and  15  c.  c. 
of  concentrated  sulphuric  acid.  This  solution  will  not  attack  the 
rubber  tube  of  a  Mohr's  burette.  Vaseline  is  probably  as  good  a 
lubricant  as  can  be  found  for  the  burette  cocks. 

Indicator  Bottles,  Spot  Plates,  Etc. — Indicators  showing  the 
end  point  of  titrations  should  be  kept  in  bottles  provided  with 
droppers.  Any  catalogue  of  chemical  supplies  will  show  several 
different  forms,  of  which  Schuster's,  provided  with  a  ground  glass 


Pig.  29. — Automatic  Pipette. 

stopper,  will  be  found  convenient.  A  bottle  through  the  cork  of 
which  a  medicine  dropper  is  inserted  may  also  be  used;  or,  in 
place  of  the  rubber-bulb  dropper,  a  piece  of  short  glass  tubing 
(5  in.)  may  be  drawn  out  to  a  point  at  one  end  and  blown  into 
a  bulb  at  the  other.  The  warmth  of  the  ringers  placed  on  the 
bulb  causes  the  air  in  the  latter  to  expand,  forcing  a  drop  or  two 
of  the  indicator  out  of  the  other  end. 

Spot  plates  of  porcelain  will  be  needed  where  outside  indi- 
cators are  used.    These  are  glazed  arid  may  be  purchased  either 


APPARATUS  FOR  TITRATIONS.  45 

with  or  without  cavities.  These  latter  plates  are  the  most  con- 
venient, as  the  drops  are  held  in  depressions  and  do  not  run 
together.  A  plate  sH  x  7  inches,  with  30  cavities,  will  be  found 
a  good  size  for  bichromate  and  ferrocyanide  titrations.  A  spot 
plate  may  be  made  by  pouring  melted  paraffine  into  a  dinner 
plate  and  allowing  it  to  cool.  This  plate  may  be  easily  cleaned 
by  washing  off  with  a  stream  of  hot  water  from  a  wash  bottle. 

Porcelain  plates  are  also  used  upon  which  to  set  beakers, 
flasks,  etc.,  in  order  to  observe  the  color  changes  during  titration. 
Flat,  square  plates  may  be  purchased  for  this  purpose,  or  dinner 
plates  or  saucers  may  be  used.  Where  titrations  are  made  at 
night,  the  following  device  is  said  to  be  useful:  A  hole  6  inches 
square  is  cut  in  the  table  just  below  the  burette,  a  ground  glass 
plate  is  fitted  over  this  and  under  the  glass  is  placed  an  incandes- 
cent lamp  with  a  white  reflector.  • 

Where  solutions  have  to  be  titrated  while  boiling,  a  small 
electric  stove  or  hot  plate  is  said  to  be  exceedingly  convenient. 


CHAPTER   VIII. 
BALANCE  SUPPORT,  BALANCE  AND  ACCESSORIES. 

Brick  Pier  Support.— It  is  essential  that  the  balance,  used  for 
analytical  work,  should  be  mounted  on  some  firm  support ;  as,  not 
only  does  the  accuracy  of  the  weighings  depend  upon  the  free- 
dom of  the  instrument  from  vibration  and  jar,  but  also  the  life  of 
the  balance  itself.  It  is  equally  important,  also,  from  the  point  of 
rapidity,  since  any  disturbance  of  the  swings  makes  a  new  trial 
necessary.  The  author  has  seen  balances  mounted  so  poorly, 
that  walking  across  the  floor,  -while  the  beam  was  oscillating, 
would  cause  a  perceptible  tremor  of  the  pointer,  and  the  slam- 
ming of  a  door,  anywhere  in  the  building,  during  the  "swingings," 
was  enough  to  throw  the  apparatus  out  of  adjustment.  The  most 
satisfactory  support  for  the  balance  is,  of  course,  a  masonry  pier 
from  the  ground.  The  usual  form  consists  of  two  brick  piers, 
about  two  feet  part  and  a  brick  and  a  half  thick,  on  which  rests 
a  slate  or  stone  slab.  Almost  every  college  laboratory  has  its 
balances  so  mounted,  and,  in  some  instances,  the  piers  run  up 
from  the  ground  to  the  second  and  third  floors.  Concrete  may,  of 
course,  be  used  in  place  of  the  brick  piers.  The  stone  slab  is 
usually  placed  high  enough  from  the  floor,  in  the  college  labora- 
tory, to  permit  of  the  student  standing  while  weighing.  In  the 
mill  laboratory,  however,  it  will  be  found  much  better  not  to  make 
the  height  so  great;  and  to  do  the  weighing  while  sitting  down. 
In  technical  laboratories  it  is  usual  to  weigh  a  large  number  of 
samples  or  crucibles  at  once,  so  that  the  operator  would  find  it 
very  fatiguing  to  stand  throughout  the  operation.  Where  the 
laboratory  is  located  on  the  first  floor  of  the  building,  the  mount- 
ing of  the  balance  is  comparatively  simple,  as  all  it  will  be  neces- 
sary to  do  is  to  erect  a  couple  of  brick  or  concrete  piers  and  to  lay 
a  slab  of  slate  across  these.  The  piers  need  not  extend  down  into 
the  ground  for  more  than  a  foot,  nor  is  it  necessary  to  make  them 
thicker  than  eight  or  ten  inches.  The  concrete  for  the  piers  is 
made  of  one  part  Portland  cement,  three  of  sand  and  from  four 
to  six  of  broken  stone  or  gravel.  It  should  be  tamped  into  the 


BALANCES  AND  ACCESSORIES. 


47 


wooden  moulds.    In  place  of  the  slate  slab  and  piers,  the  all  con- 
crete table,  Fig.  31,  described  a  little  further  on,  may  be  used. 

Where  a  cellar  comes  below  the  laboratory  it  will  probably 
be  better  to  build  one  solid  piece  of  masonry,  24  x  18  inches,  from 
the  ground  up,  and  bolt  to  this  a  slate  slab,  28  x  28  inches ;  so  that 
it  projects  ten  inches  in  front  of  the  pier.  Or  else  a  pier  30  x  18 
inches  may  be  built  from  the  ground  to  the  floor,  and,  on  either 
end  of  this,  two  narrow  piers,  18  x  6  inches  erected.  A  slab  of 
slate,  36  x  20  inches,  is  then  to  be  laid  over  these.  Slate  slabs  for 
this  purpose  need  not  be  thicker  than  i^  to  2  inches.  Where 
slate  or  stone  slabs  can  not  be  obtained,  a  top  of  two-inch  seasoned 
and  neatly  dressed  board  may  be  made  to  serve  instead.  As 


JSL 


Floor 


Fig.  30. — Iron  Column  Support  for  Balance. 

the  board  is  not  heavy  enough  to  stay  down  of  its  own  weight,  it 
must  be  bolted  to  the  pier.  This  may  be  done  by  bolting  the  bat- 
tens to  the  pier  and  then  screwing  the  top  to  the  former.  The 
screws  should  be  sunk  about  an  inch  below  the  level  of  the  surface 
and  the  holes  then  stopped  up  with  a  round  peg  and  glue,  and  the 
whole  smoothed  off  with  a  plane  and  sandpaper.  Or  the  top  may 
be  bolted  directly  on  to  the  pier,  and  the  bolts  so  arranged  as  to 
come  out  of  the  way,  under  the  balance. 

Iron  Column  Support. — Figure  30  shows  a  simple  way  of 
mounting  a  balance  solidly.  It  consists  of  a  wooden  top  fastened 
to  two  battens,  which  are  in  turn  bolted  to  four  iron  columns, 
which  are  imbedded  in  concrete  in  the  ground.  The  columns  are 


SMALL    CHEMICAL    LABORATORIES. 


made  from  2  or  3-inch  wrought  iron  pipe  by  flattening  and  bend- 
ing. Any  blacksmith  can  make  them.  The  concrete  piers  are 
only  large  enough  to  give  the  necessary  stability  and  need  not 
come  above  the  ground.  If  made  12  x  18  x  36  inches,  they  will  be 
of  ample  size.  The  battens  are  first  bolted  to  the  columns,  the 
heads  of  the  bolts  being  sunk  below  the  upper  surface  of  the  bat- 
tens ;  the  latter  being  trued  up  so  as  to  make  the  table  top  level, 
by  the  use  of  metal  liners.  The  top,  which  should  be  made  of 
well  seasoned  2-inch  lumber,  is  then  fastened  to  the  battens  by 
means  of  screws,  from  below.  In  order  to  get  the  columns  in 
proper  position  in  the  concrete,  it  will  be  found  simplest  to  make 
a  rough  frame  and  bolt  the  columns  to  this,  so  that  their  tops  are 
all  on  a  level,  and  then  to  pour  the  concrete  into  the  moulds  and 


„  -  TS  Iron  ffods 


,  -i'/ron  Rods 


Floor' 


Fig.  31.— All  Concrete  Balance  Support. 

around  the  lower  ends  of  the  pipes.  The  table  top  may  be  filled 
and  varnished  and  the  pipe  columns  should  be  painted  with  alum- 
inum paint- — such  as  is  used  for  radiators,  etc. — or  with  black 
asphalt  varnish.  Where  a  plank  top  is  used  for  a  balance  table, 
particularly  if  this  is  made  of  white  pine  or  other  soft  wood,  the 
legs  of  the  balance  case  are  apt  to  sink  into  the  wood,  and  it  is 
therefore  well  to  rest  the  legs  upon  small  pieces  of  metal,  such  as 
one-cent  pieces. 

Solid  Concrete  Support. — Figure  31  shows  the  arrangement 
for  mounting  the  balances  in  the  laboratories  of  the  Dexter  Port- 
land Cement  Company.  The  laboratories  are  on  the  second  floor, 
and  the  balance  room  is  built  above  a  large,  fireproof,  concrete 
vault,  used  for  the  storage  of  the  books,  papers,  etc.,  of  the  office 
below.  On  the  roof  of  this  vault  a  concrete  table  for  the  bal- 


BALANCES  AND  ACCESSORIES.  49 

ances  has  been  built.  Its  construction  is  evident  from  the  illus- 
tration. The  concrete  was  made  of  a  mixture  of  one  part  Port- 
land cement  and  four  parts  limestone  screenings.  The  upper 
surface  of  the  table  was  trowelled,  while  the  concrete  was  still 
wet,  until  it  presented  a  smooth  glassy  surface.  A  wooden  form 
was,  of  course,  first  made,  iron  rods  were  inserted  as  shown  in 
the  cut,  and  the  concrete  was  poured  into  this  form,  and  tamped 
and  trowelled  as  usual.  The  wooden  forms  should  be  fastened 
together  with  screws  to  avoid  breaking  off  the  corners  and  edges 
of  the  table,  in  removing  the  boards.  This  concrete  table  pre- 
sents a  pleasing  appearance  to  the  eye  and  is  satisfactory  in 
every  way. 

Shelf  Support. — The  rigid  mounting  of  balances  in  labora- 
tories located  on  the  upper  floors  of  factories  and  other  build- 
ings often  presents  a  problem  difficult  of  solution.  If  the  building 
is  of  brick  or  stone,  the  best  plan  will  be  to  rest  the  balance  on  a 
shelf  supported  from  the  outer  wall  by  iron  or  heavy  wooden 
brackets,  bolted  fast  to  the  former.  In  factory  or  mill  buildings, 
much  of  the  shafting  is  supported  by  the  girders  and  beams  of 
the  floor  above,  and  consequently  the  latter  trembles  more  or  less 
all  the  time  when  the  machinery  is  in  operation.  Where  the 
laboratory  is  on  such  a  floor,  it  is  almost  an  impossibility  to  make 
a  weighing  when  the  balance  merely  rests  on  a  table.  In  such 
cases,  if  it  is  impossible  to  bolt  a  shelf  on  to  another  wall,  the 
following  arrangement  may  be  resorted  to,  and  will  deaden  the 
vibrations  to  a  certain  extent.  First,  a  very  heavy  wooden  table 
is  made  and  on  this  is  placed  a  slab  of  slate,  stone  or  even  metal, 
resting  on  six  or  more  solid  rubber  balls  an  inch  and  a  half  or 
two  inches  in  diameter.  The  heavy  slab  takes  up  much  of  the 
jar.  The  addition  of  another  slate  slab,  resting  on  rubber  balls, 
which  in  turn  rest  on  the  first  slab,  will  still  further  lessen  the 
jar.  As  the  weight  of  the  slab  flattens  the  rubber  balls  some- 
what, it  is  not  necessary  to  scoop  out  depressions  in  the  table  or 
slab  in  which  they  may  rest.  When  a  table  is  made  use  of  to 
support  the  balance  it  should  be  made  heavy  and  substantial. 

Location  of  the  Balance  Support. — The  balance  table  or  sup- 
port should  be  placed  in  a  good  light  but  not  where  the  sun  will 
ever  shine  directly  upon  it.  If  it  must  be  placed  by  a  window 
which  would  permit  the  sunlight  to  fall  upon  it,  the  former  should 
be  provided  with  a  screen  or  awning  to  prevent  this. 


5o  SMALL    CHEMICAL    LABORATORIES. 

Balance  Support  Bench.— Figure  32  shows  a  small  bench  or 
seat  for  use  with  the  balance  table.  Its  form  is  evident  from  the 
cut.  It  is  made  of  %-inch  boards  and  its  dimensions  are — width, 
14  inches;  length,  16  inches;  height,  18  inches.  The  small  hand 
hole  in  the  top  of  the  bench  is  to  carry  it  about  by.  A  table  made 
similar  to  this  only  larger  and  of  much  heavier  lumber  will  also 
make  a  good  balance  table.  In  this  case  the  dimensions  should 
be  about  as  follows : — width,  20  inches ;  length,  30  inches ;  height, 
30  inches. 

The  Balance. — It  is  perhaps  well  here  to  say  something  about 
the  balances  themselves.  Two  general  types  of  balances  are  on 
the  market  in  this  country.  In  the  first  of  these  types,  shown 
in  Fig.  33,  the  beam  itself  is  graduated  to  receive  the  rider 


Fig.   32.— Laboratory   Bench   or   Stool. 

directly,  and  is  made  in  the  form  of  a  very  much  flattened  isosceles 
triangle  with  the  apex  pointing  downward.  The  balances  manu- 
factured by  Becker's  Sons  (Rotterdam),  Christian  Becker  (New 
York),  H.  Kohlbush  (New  York),  Henry  Troemner  (Philadel- 
phia), and  Wm.  Ainsworth  (Denver),  all  have  the  characteristics 
of  this  type.  In  the  second  type,  shown  in  Fig.  34,  the  rider 
moves  upon  a  scale  separate  from  and  fastened  to  the  beam,  and 
the  latter  is  in  the  form  of  an  isosceles  triangle,  much  more 
acute  than  in  the  former  type,  and  with  the  apex  of  the  triangle 
pointing  up.  Sartorius  and  Staudinger,  Arthur  H.  Thomas  Co., 
Agents,  Philadelphia,  balances  are  representative  of  this  type. 
Balances  of  first  type  are  the  more  used,  however,  in  mill,  fur- 
nace, and  smelter  laboratories,  in  this  country.  Enough  money 


BALANCES  AND  ACCESSORIES. 


Fig.  33. — Analytical  Balance — Becker's  Sons 


Fig.  34.— Analytical  Balance— Staudinger. 


52  SMALL    CHEMICAL    LABORATORIES. 

shorld  always  be  put  in  a  balance  to  get  a  good  one.  This  does 
not  mean  a  showy  one,  but  one  which  will  do  accurate  work 
under  the  trying  conditions  of  technical  analysis.  The  short 
beam  balances  will  be  found  accurate  enough  for  technical  work 
and  they  are  much  more  rapid.  Nothing  is  gained  by  having  an 
analytical  balance  which  will  be  sensitive  to  less  than  o.i  milli- 
gram with  a  load  of  100  grams,  since  this  is  a  degree  of  accuracy 
seldom  reached  by  the  other  operations  of  a  technical  analysis. 
For  assay  work,  however,  button  balances,  sensitive  to  o.oi  milli- 
gram are  desirable.  A  balance  with  an  aluminum  beam  is  to  be 
preferred  to  one  made  of  brass,  since  the  lighter  the  beam  the 
greater  sensibility  the  balance  possesses.  The  knife  edges  should 
be  preferably  of  agate,  and  the  planes  always  of  agate. 

The  arrangement  of  the  arrest  of  beam  and  pans  should  be 
such  that  when  the  balance  is  at  rest,  the  knife  edges  and  planes 
are  not  in  contact;  and  if  the  pan  arrest  moves  in  the  same  arc 
as  the  beam  itself  it  is  a  point  in  favor  of  the  balance,  as  the  dull- 
ing of  the  knife  edges  by  dragging  them  across  the  planes,  which 
happens  when  the  weight  in  one  pan  is  two  or  three  grams  heavier 
than  the  other,  is  avoided.  The  balance  should  be  preferably 
mounted  on  a  glass  plate. 

Assay  Balances. — These  are  of  two  kinds — button  balances 
and  pulp  balances.  The  former  are  used  for  weighing  the  buttons 
of  gold  and  silver  obtained  by  cupellation  and  the  latter  are  for 
weighing  the  samples  of  ore.  Button  balances  are  made  much  moi  c 
sensitive  than  analytical  balances  and  are  intended  for  weign- 
ing  only  a  few  milligrams.  The  pans  are  much  smaller,  are  con- 
cave and  removable  and  the  beam  is  much  lighter.  They  are  now 
usually  made  with  the  rider  attachment.  Troemner  and  Ains- 
worth  both  make  assay  balances  sensible  to  1-500  of  a  milligram. 
For  ordinary  purposes  a  balance  sensible  to  1-50  of  a  milligram 
will  be  sufficient.  All  the  bearings  of  this.,  however,  should  be 
of  agate.  Small  platinum  weights,  I  milligram  and  up,  are  used. 
F.  W.  Thompson,  of  Denver,  Colo.,  makes  an  assay  balance,  in 
which  all  of  the  small  weights  (72  milligrams)  are  in  the  form  of 
riders.  These  are  so  suspended  from  a  carrier  that  they  may  any 
or  all  of  them  be  dropped  over  a  projecting  arm  on  the  wire  sus- 
pending-the  right  hand  pan.  This  does  away  with  handling  the 
small  weights. 

Any  balance  sensible  to  two  or  three  milligrams  and  having  a 


BALANCES  AND  ACCESSORIES.  53 

capacity  of  two  or  three  hundred  grams  will  answer  as  a  pulp 
balance. 

Weights. — The  weights  must,  of  course,  be  accurate,  and  a 
new  balance  and  weights  should  always  be  tested.  'It  is  not 
necessary  for  ordinary  technical  analysis  that  the  arms  of  the 
balance  shall  be  of  equal  length,  nor  that  the  weights  should  be 
compared  with  the  standards  in  Washington,  but  the  balance 
should  be  sensitive  to  at  least  0.2  milligrams  with  a  load  of  50 
grams  on  each  pan,  and  still  better,  to  o.i  milligram  with  a  load 
of  200  grams.  The  latter  requirement  is  enough  for  all  analytical 
purposes.  It  is  also  essential  that  the  weights  should  be  relatively 
correct  with  regard  to  each  other;  that  is,  the  lo-gram  weight 
must  be  equivalent  to  exactly  ten  times  the  weight  of  the  i-gram 
piece,  etc. 

Balances  for  Rough  Weighing. — In  every  laboratory  there 
will  be  needed  a  balance  capable  of  weighing  quickly  and  roughly 
200  or  300  grams  of  salts  to  be  used  in  making  up  solutions.  The 
balances  with  the  pans  above  the  beam  will  be  found  the  most 
convenient  of  these.  The  torsion  balances  are  made  to  cover  a 
wide  range  of  work : — for  example  these  can  be  obtained  with 
pans  4  inches  in  diameter,  a  capacity  of  500  grams  and  a  sensi- 
bility of  5  milligrams,  or  with  6-inch  pans,  a  capacity  of  5  kilo- 
grams and  a  sensibility  of  l/2  gram.  The  latter  may  be  obtained 
with  beam  graduated  to  ^  gram.  The  "Harvard  Trip  Balance" 
is  also  convenient.  This  has  6-inch  porcelain  plates  in  place  of 
pans  and  a  graduated  beam  (i-io  gram  to  10  grams).  It  is 
sensible  to  i-io  gram  and  has  a  capacity  of  I  kilogram.  "Troem- 
ner's  New  Laboratory  Scale"  is  also  well  suited  to  this  work.  It 
has  6-inch  pans,  a  capacity  of  200  grams  and  is  sensitive  to  1-20 
gram.  The  weights  are  kept  on  a  projecting  shelf  at  the  base  of 
the  balance.  The  Harvard  and  torsion  balances  will  need  a  set 
of  cheap  weights  ranging  from  200  grams  to  I  gram. 

Pans,  Etc. — In  most  technical  laboratories,  it  is  usual  to 
weigh  out  an  exact  amount  of  a  substance;  and  for  this  purpose 
counterpoised  watch-glasses  are  usually  used.  That  is,  two 
watch-glasses  balanced  against  each  other.  These  can  be  bought 
of  any  dealer  in  balances  or  chemical  supplies ;  but,  if  the  chemist 
desires,  he  can  make  a  pair  himself  from  ordinary  watch-glasses, 
by  selecting  from  his  stock  the  two  which  agree  most  closely  in 
weight,  and  grinding  and  filing  until  they  balance.  If  they  are 


54  SMALL    CHEMICAL    LABORATORIES. 

to  be  left  on  the  pans  when  crucibles  are  weighed,  the  final  adjust- 
ment of  this  may  be  done  with  the  aid  of  the  screws  on  the  end  of 
the  balance  beam. 

Where  a  sample  has  to  be  transferred  to  a  flask,  it  is  neces- 
sary, if  a  watch-glass  is  used,  to  brush  the  sample  from  this  on  to 
a  piece  of  glazed  paper,  and  then  from  this  in  turn  to  the  flask. 
To  avoid  the  double  operation  and  chance  of  loss  of  the  sub- 
stances, it  will  be  found  best  to  substitute  a  pair  of  counterpoised 
celluloid  pans  for  the  watch-glasses.  These  are  made  by  cutting 
out  squares  of  thin  clear  celluloid,  with  rounded  corners,  large 
enough  to  completely  cover  the  balance  pans.  These  can  be 
curved  between  the  fingers,  to  fit  the  mouth  of  the  flask,  and  the 
sample  brushed  from  them  directly  into  the  flask.  Aluminum  foil 
may  also  be  used  for  these  pans.  If  a  watch-glass  is  used  it 
should  completely  cover  the  pan,  so  as  to  avoid  danger  of  the 
material  dropping  on  the  pan  and  being  included  in  the  weight 
but  not  in  the  sample. 

To  transfer  the  sample  to  the  pan  and  remove  the  excess,  a 
small  spatula  is  used.  This  should  be  ground  down  on  an  emery 
wheel  or  grind-stone  so  it  tapers  to  a  rounded  point  of  about 
^-inch  width.  When  it  is  to  be  used  for  iron  and  steel  analysis, 
it  should  be  magnetized  by  rubbing  across  the  poles  of  a  bar 
magnet  or  dynamo.  In  weighing  pig  iron  samples,  however,  care 
should  be  used  not  to  do  anything  more  than  get  the  final  adjust- 
ment to  the  weight  by  the  use  of  its  magnetic  properties,  as  the 
non-magnetic  particles  of  the  sample  contain  a  larger  proportion 
of  the  metalloids  than  do  the  magnetic  ones,  and  an  undue  pro- 
portion of  the  former  may  be  left. 

To  brush  the  sample  from  the  watch-glass  or  celluloid  pans, 
use  a  flat  sable  or  camel's  hair  brush,  ^4  to  I  inch  wide.  To 
transfer  the  sample,  rap  the  glass  or  pan  gently  with  the  brush 
handle,  until  most  of  the  material  falls  into  the  dish  or  flask,  and 
then  brush  in  the  few  particles  which  remain  attached. 

In  water  analysis,  alkali  determinations,  etc.,  where  a  residue 
of  deliquescent  salts,  left  from  evaporation,  has  to  be  weighed  in 
a  platinum  dish,  it  will  be  found  almost  an  impossibility  to  get  an 
exact  weight  owing  to  the  absorption  of  moisture  from  the  air  by 
the  contents  of  the  dish.  A  useful  adjunct  of  the  balance  will 
therefore  be  an  aluminum  box,  with  cover,  large  enough  to  hold 
the  dish.  Such  boxes  are  sold  for  holding  soap,  salves,  etc.,  and 


BALANCES  AND  ACCESSORIES.  55 

while  the  covers  do  not  fit  tight  enough  to  make  them  air-tight, 
they  do  fit  tight  enough  to  keep  the  moisture  of  the  air  from 
coming  in  contact  with  the  contents  of  the  dish  during  the  short 
time  necessary. to  make  a  weighing.  The  box  may  be  counter- 
poised by  a  small  piece  of  brass,  filed  down  to  balance  it ;  or  the 
dish  and  box  may  be  weighed  together.  In  use  the  box  should 
be  dried  in  the  desiccator  while  the  dish  is  cooling.  When  the 
dish  and  contents  are  cool,  they  are  to  be  placed  in  the  box,  the 
cover  fitted  on  and  the  weight  immediately  taken.  If  an  alum- 
inum box  can  not  be  obtained  a  seamless  tin  box  such  as  is  used 
for  salve  or  blacking  may  be  employed.  It  is  much  heavier  than 
the  aluminum  box,  however,  and  in  large  sizes  so  much  so  as  to 
prevent  it  being  used. 

Where  hygroscopic  substances  have  to  be  weighed,  weighing 
bottles  will  be  needed.  These  may  be  purchased  with  light  blown 
glass  stoppers  and  in  a  variety  of  forms,  preferably  with  flat  bot- 
toms and  straight  sides.  When  samples  of  ore,  etc.,  are  to  be 
weighed,  a  small  bottle  25  mm.  in  diameter  and  40  mm.  high  will 
be  found  convenient.  If  the  sides  of  the  bottle  are  straight  the 
sample  can  be  brushed  from  the  bottle  with  a  round  camel's  hair 
brush.  These  little  bottles  can  also  be  obtained  in  a  squat  form, 
as  wide  as  70  mm.  and  as-  low  as  30  mm.  Such  weighing  bottles 
are  well  adapted  to  weighing  the  residues  from  evaporation  and 
drying,  both  operations  being  conducted  in  them.  They  should  be 
cooled  in  the  desiccator  with  stopper  out.  In  weighing  the  bot- 
tles the  stopper  should  always  be  removed  for  a  second,  just 
before  weighing,  to  allow  the  pressure  to  equalize.  Counter- 
poised filter  papers  are  usually  supposed  to  be  weighed  between 
watch-glasses  held  together  with  clips.  A  weighing  bottle  70  mm. 
high  and  30  mm.  in  diameter  will  be  found  much  better,  as  it  is 
lighter.  This  size  will  take  an  cm.  filter  paper.  Hygroscopic 
precipitates  may  be  weighed,  crucible  and  all,  in  such  a  bottle. 
To  give  an  idea  of  the  lightness  of  these  little  blown  glass-stop- 
pered weighing  bottles,  one  which  the  author  has,  measuring  50  x 
30  mm.  and  holding  30  c.  c.  weighs  only  18  grams. 


CHAPTER   IX. 
HEATING  APPLIANCES. 

General  Considerations.— If  the  laboratory  is  so  located  that 
coal  gas  or  natural  gas  is  accessible,  the  problem  of  heating  hot 
plates  and  making  ignitions  simply  resolves  itself  into  the  use  of 
gas  stoves  and  burners  of  the  simplest  types,  such  as  are  familiar 
to  every  student  of  chemistry.  When,  however,  the  laboratory  is 
located,  as  most  small  ones  are,  at  some  mine,  smelter  or  furnace, 
no  such  convenient  means  is  at  hand  and  something  must  be  sub- 
stituted for  city  gas.  Where  fire  assays  are  made,  the  chemist 
will  of  course  find  the  muffle  of  the  assay  furnace  all  that  is 
needed  for  burning  off  his  filter  papers  and  igniting  his  precipi- 
tates; and  oil  stoves  or  stoves  heated  by  wood  or  coal  may  be 
used  to  evaporate  solutions,  boil  water,  etc.  In  the  east,  in  the 
laboratories  of  blast  furnaces,  cement  mills  and  various  and  sundry 
manufactories,  there  are  of  course,  no  fire  assays  made  and  the 
heating  here  is  usually  done  with  gasolene. 

This  is  used  in  one  or  two  ways ;  either  the  gasolene  is  burned 
directly  in  a  suitable  burner  or  lamp,  or  else  it  is  vaporized  by  a 
current  of  air  and  the  mixture  is  burned  in  some  form  of  Bunsen 
burner  just  as  if  it  was  coal  gas.  The  latter  method  is  the  most 
convenient  one  but  requires  the  use  of  a  generator  to  vaporize 
the  gasolene.  The  latter  is  somewhat  expensive  if  purchased, 
but  in  many  cases  may  be  constructed  by  the  mechanics  employed 
at  most  manufacturing  plants  at  a  comparatively  small  cost.  The 
lamps  for  burning  gasolene  directly  are  troublesome  and  not 
.altogether  free  from  danger,  unless  carefully  handled.  They  re- 
quire frequent  attention,  and  usually  have  to  be  filled  at  least  once 
a  day. 

Gasolene  Lamps. — Of  these  lamps  the  best  known  is  that  of 
Dangler,  which  is  shown  in  Fig.  35.  In  order  to  start  the  lamp 
the  reservoir,  A,  is  filled  with  gasolene,  the  bulb,  B,  is  compressed 
a  few  times  to  put  the  gasolene  under  pressure  and  the  valve,  C, 
is  opened  enough  to  let  a  little  gasolene  into  the  pan  D;  this  is 
then  ignited  with  a  match  and  when  the  burner  has  been  heated, 
the  gasolene  is  turned  on,  vaporized  by  the  hot  burner  and  ignited 


HEATING  APPLIANCES. 


57 


at  E.  These  lamps  give  a  flame  which  can  be  regulated  from 
the  size  of  that  of  an  ordinary  Bunsen  burner  to  a  powerful  blast. 
They  cost  between  $5.00  and  $6.00,  can  be  purchased  from  any 
supply  house,  and  are  very  similar  to  the  torches  used  by  painters, 
plumbers,  etc. 

Figure  36  shows  the  burner  manufactured  by  The  Hoskins 


Fig.  35. — Dangler's  Gasolene  Lamp. 


"••"f"-  ~T 

Fig.  30. — Hoskins'  Gasolene  Lamp.        Fig.   37.— The   Jewel   Gasolene   Lamp. 

Company,  93  Erie  St.,  Chicago.  This  burner  is  an  improvement 
on  the  Dangler  burner.  It  is  more  portable  and  the  substitution 
of  the  metal  pump  for  the  rubber  bulb,  which  wears  out  rapidly, 
is  a  good  feature.  The  flame  is  under  perfect  control  and  the 
lamp  is  substantially  put  up.  The  extra  tubes  are  for  a  fish  tail 
flame,  for  bending  glass,  and  one  horizontally  directed. 

Figure  37  shows  the  Jewel  gasolene  lamp  for  sale  by  E.  H. 
Sargent  &  Co.,  Chicago.    This  is  a  very  small,  new  type  of  gaso- 


58  SMALL    CHEMICAL    LABORATORIES. 

lene  burner  which  meets  all  the  purposes  of  a  Bunsen  burner.  It 
generates  its  own  gas  and  is  practically  automatic  in  operation. 
The  tank  or  reservoir  which  forms  the  main  body  of  the  lamp 
holds  about  one-half  pint  of  gasolene.  Air  pressure  for  operating 
this  torch  is  obtained  by  means  of  a  small  force  pump  contained 
in  the  handle.  The  flame  is  adjustable  in  size  from  almost  noth- 
ing to  5  to  6  inches-,  and  will  burn  about  i  *4  hours  at  full  blast  from 
one  filling  of  the  reservoir.  The  ease  with  which  this  burner  is 
lighted  is  a  most  desirable  feature.  The  heat  of  one  or  two 
matches  is  all  that  is  necessary  to  generate  the  burner.  Figure 
38  shows  the  generator  being  heated  preparatory  to  lighting  the 
burner. 

Stoves, — For  evaporating  solutions,  etc.,  a  gasolene  stove 
such  as  is  used  in  kitchens  will  be  found  a  necessary  adjunct  to 
the  gasolene  lamps.  Or  a  kerosene  stove  may  be  used.  These 


Fig.  38.— Lighting  the  Jewel  Lamp. 

latter  can  be  obtained  either  with  or  without  wicks,  the  wick- 
less  "blue  flame"  ones  being  the  best,  although  a  little  more  expen- 
sive than  the  older  form.  These  stoves  are  usually  mounted  on 
an  iron  frame  and  are  intended  to  stand  directly  on  the  floor.  It 
will  be  found  most  convenient,  however,  to  raise  the  stove  six  or 
more  inches  and  to  build  a  hood  over  it.  The  stove  should  be 
covered  with  a  cast  iron  plate  and,  if  many  samples  have  to  be 
dried  or  moisture  determinations  made,  the  ovens  sold  with  these 
stoves  for  baking  purposes  may  be  used. 

In  place  of  the  oil  or  gasolene  stove,  an  ordinary  wood  or 
coal  cooking  stove  may  be  used,  or  a  hot  plate  may  be  rigged  up 
over  a  grate,  so  as  to  be  heated  by  wood  or  coal.  Neither  of  these 
schemes  are  desirable,  however,  except  where  kerosene  and  gaso- 
lene can  not  be  obtained.  Mr.  Herbert  Haas  describes  such  an 
arrangement1  designed  by  him  for  the  laboratory  of  a  pyrite 
smelter  in  California,  as  follows : 


Electrochemical  Industry,   III.,   3,   101. 


HEATING  APPLIANCES. 


59 


it uf.'.. 

Fig.  39.— Laboratory  Hearth  Using  Wood  for  Fuel— Haas. 


60  SMALL    CHEMICAL    LABORATORIES. 

"The  hearth,  Fig.  39,  rests  on  the  ground  and  the  flue  from 
it  is  filled  with  ashes  and  earth  to  within  18  inches  of  the  hot- 
plate. In  front  of  the  ash-pit,  beneath  floor,  is  a  12  x  inch  inch 
opening,  which  is  closed  wih  a  piece  of  sheet  iron  luted  on  with 
clay.  The  accumulated  ashes  in  the  ash-pit  are  removed  through 
this  opening,  thus  avoiding  their  removal  through  the  office.  The 
ash-pit  door,  shown  in  the  drawing,  is  used  solely  to  regulate  the 
draft.  Old  rails,  preferably,  are  used  as  grate  bars.  . 

"The  front  elevation  of  the  hearth  is  shown  in  the  illustra- 
tion, which  includes  also  the  elevation  of  the  fireplace  front,  with 
the  ash-pit  door  and  the  feed  door.  The  lines  AB  and  CD,  explain 
the  respective  elevations.  The  walls  of  the  hearth  consist  of  one 
course  of  brick,  excepting  at  the  stack,  which  is  of  a  course  and  a 
half,  and  the  fire-box,  which  is  of  two  courses.  These  walls  sup- 
port the  hot-plate,  having  its  upper  surface  43  inches  above  the 
level  of  the  floor.  A  detailed  dimensioned  drawing  of  the  hot- 
plate is  given  in  the  lower  part  of  the  drawing.  The  plate  is  cast 
in  two  pieces,  having  a  lap  so  that  a  tight  joint  may  be  obtained, 
and  at  given  intervals  ribs  are  cast  as  a  safeguard  against  warp- 
ing. A  circular  hole,  over  which  the  still  is  placed,  is  left  in  the 
plate.  -A  portion  of  the  hot-plate  2.5  feet  by  6  feet  8  inches,  is 
covered  with  a  hood,  which  rests  on  one  layer  of  bricks,  except  at 
the  hottest  parts,  where  there  are  two  layers  in  order  to  protect 
the  wood.  The  back  side  of  the  hood  does  not  rest  on  bricks,  but 
is  separated  from  the  plate  by  a  2-inch  air  space  extending  the 
entire  length  of  6  feet  8  inches.  Access  to  the  hot-plate  is  ob- 
tained through  two  windows,  each  having  twelve  lights  of  glass 
and  hinge  on  the  butts.  The  hood  is  tightly  ceiled  with  tongue  and 
groove  lumber,  and  has  an  18  x  18  inch  wooden  chimney,  10  feet 
high,  to  carry  off  the  fumes.  The  temperature  of  the  inside  of  the 
hood  and  hood  chimney  is  sufficient  to  draw  in  fresh  air  constant- 
ly and  thus  improve  the  ventilation  of  the  laboratory. 

"The  great  advantage  of  the  hot-plate  is  in  its  gradual  de- 
crease in  temperature  towards  the  chimney.  The  heating  of  solu- 
tions is  generally  started  at  the  coolest  place,  and  gradually  con- 
tinued toward  the  hottest  part.  The  heat  is  diffused  over  a  large 
area,  and  is  not  concentrated  at  one  small  spot,  as  is  the  case 
with  a  Bunsen  burner;  and  the  boiling  over  of  solution  is  thus 
easily  avoided  at  the  expenditure  of  the  least  attention  and  care; 
this  allows  the  chemist  time  in  which  to  attend  to  other  work.  A 


:  TIXG  APPLUXCES. 


6l 


small,  uncovered  portion.  _  \\  3  feet  4  inclu  - 

for  operations  which  are  preferably  conducted  in  the  open  air. 

"A  still,  placed  over  the  circular  hole  described  above,  pro- 
vides the  laboratory  with  about  14  gallons  of  distilled  water  daily. 
The  still  now  used  is  called  the  Cuprigraph  Sanitary  Still.  Xo.  II, 
and  when  once  regulated  requires  very  little  additional  attention. 
The  hearth  tr  -  es  two  purposes,  one  to  provide  the  labora- 
tory with  distilled  water,  and  the  other  to  give  the  chemist,  at  the 
same  time,  a  very  efficient  way  of  heating  solutions.  The  distilla- 
tion of  the  water  utilizes  much  of  the  heat,  yet  the  hearth  is  nec- 
essarily wasteful,  the  flue  being  too  short  for  economizing  fuel. 
The  weekly  fuel  consumption,  hov>  -  only  from  one-half  to 


Fig.  40.— Springfield  Gas  Machine. 

three-quarters  of  a  cord  of  wood,  which  at  $4.00  a  cord  is  equiva- 
lent to  an  operating  expense  of  from  28  to 

Gas  Machines. — Of  the  machines  for  generating  "gasolene 
ingheld"  is  perhaps  the  best  known  and  is  manu- 
factured by  The  Gilbert  &  Barker  Manufacturing  Co.,  80  and  82 
Fourth  Ave..  Xew  York.  The  Springfield  gas  machine  consists 
of  a  gas  generator,  which  consists  of  a  cylinder  containing  evapor- 
ating pans  or  chamber-  lator  for  mixing  the  air  and  vapor 
in  the  proper  proportions,  and  an  automatic  air-forcing  apparatus. 

The  general  plan  of  setting  the  apparatus,  and  the  arrange- 
ment of  connecting  pipes,  is  shown  in  Fig.  40,  which  illustrates  a 
Springfield  gas  machine,  set  up  and  connected,  in  every  particu- 
lar, in  accordance  with  the  latest  rules  of  the  rk  Board 
of  Fire  Underwriters.  The  automatic  air  pump  is  here  seen  in 


62  SMALL    CHEMICAL    LABORATORIES. 

the  cellar  of  the  laboratory,  and  connected  to  it  and  running  in  the 
ground  is  the  air-pipe  conveying  air  from  this  instrument  to  the 
gas  generator,  located  underground,  and  removed  from  the  build- 
ing thirty,  fifty,  one  hundred  feet,  or  more. 

When  the  machine  is  in  operation,  the  pump  forces  a  current 
of  air  through  the  generators ;  here  it  becomes  carburetted,  thus 
forming  a  combustible  gas  that  is  returned  to  the  cellar,  where  it 
passes  through  the  regulator  and,  if  too  rich  in  gasolene,  air  is 
added  to  make  the  mixture  about  15  per  cent,  gasolene  vapor  and 
85  per  cent.  air.  From  the  mixer  the  gas  goes  to  the  burners. 

Gas  is  generated  only  as  fast  and  in  such  quantities  as  is  re- 
quired for  immediate  consumption.  The  process  is  continuous 
while  the  burners  are  in  use,  but  instantly  stops  when  the  lights 
are  extinguished.  One  gallon  of  gasolene  will  make  about  one 
thousand  cubic  feet  of  gas. 

In  place  of  the  air  pump  operated  by  a  weight,  one  run  by 
water  can  be  substituted.  This  latter  form  is  to  be  preferred,  as 
it  does  not  need  any  attention.  It  does  not  require  any  head  of 
water  to  operate,  and  two  gallons  of  water  are  said  to  be  suf- 
ficient to  run  one  burner  one  hour.  Both  forms  of  pump  give  a 
steady  pressure.  These  gas  machines  give  excellent  service  and 
very  little  trouble. 

A  machine  which  gives  good  results  but  which  is  not  quite 
so  convenient  is  described  below.  It  is  similar  in  the  main  to  one 
designed  for  the  laboratory  of  the  Edison  Portland  Cement  Co. 
by  the  author.  The  generator  is  shown  in  Fig.  41.  It  consists  of 
an  ordinary  galvanized  iron  tank,  such  as  is  used  in  connection 
with  kitchen  ranges  for  holding  hot  water.  A  hole  large  enough 
to  admit  the  hand  is  cut  in  the  side  of  this  tank  at  B,  and  two 
semi-circular  pieces  of  light  angle  iron,  bent  to  conform  to  the 
inside  of  the  generator,  are  bolted  inside  as  shown  at  h.  The 
upper  side  of  these  angle  irons  are  punched  with  holes,  as  illus- 
trated in  the  small  sectional  drawing,  and  in  these  stout  wires  are 
fastened  to  make  a  sort  of  grid  across  the  tank.  Pieces  of  lamp 
wick,  d,  d,  d,  etc.,  long  enough  to  reach  to  the  bottom  of  the 
tank  are  hung  down  over  these  iron  wires  and  the  hole  B  is  then 
covered  by  bolting  on  it  a  piece  of  metal.  The  joints  of  this,  and 
also  of  all  piping,  are  covered  with  solder,  so  as  to  prevent  any 
possibility  of  a  leak.  The  air  pipe,  E,  and  the  gas  pipe,  F,  and  the 
fill  pipe,  G,  should  all  have  been  screwed  in  place  before  hanging 


HEATING  APPLIANCES.  63 

the  wick  over  the  wires.  The  tank  is  now  buried  in  the  ground, 
The  pipe,  F,  should  of  course  run  to  the  laboratory  and  connect 
with  the  gas  jets.  The  fill  pipe,  G,  should  reach  8  or  10  inches 
above  the  ground  and  be  closed  by  a  cap  containing  a  washer. 
The  pipe,  E,  leads  to  the  air  pump  to  be  described  later.  The 
generator  is  filled  with  gasolene  to  a  height  of  about  18.  inches 
from  the  bottom,  and  fresh  gasolene  added  every  day  or  so  to 
make  up  for  that  used.  The  height  to  which  the  gasolene  has 
risen  in  tfye  generator  may  be  ascertained  by  fastening  a  small 
test  tube  on  to  a  piece  of  stout  iron  wire,  and  noticing  at  what 
point  this  comes  up  full,  when  lowered  into  the  tank,  through  the 
fill  pipe,  G.  (In  putting  in  the  wires  care  should  be  exercised  to 
allow  room  between  the  wires  and  wicking,  at  this  point,  to  lower 
the  tester.) 

For  furnishing  the  air  for  this  generator  a  number  of  devices 
may  be  used.  If  only  three  or  four  burners  are  used  at  one  time 
and  a  head  of  water  is  at  hand  nothing  will  be  found  so  conven- 
ient as  the  water  blower  described  in  Chapter  V..  If  more  than 
this  number  of  burners  are  to  be  used  and  plenty  of  water  is 
at  hand  two  or  more  of  these  blowers  may  be  used,  or  a  larger 
pipe  or  iron  tank  may  be  substituted  for  the  pipe,  B  (Fig.  22), 
a  larger  over-flow  pipe  used  and  several  aspirators  screwed  into 
this  tank.  One  or  more  of  these  aspirators  may  be  used  as  the 
amount  of  work  done  in  the  laboratory  requires  it. 

In  place  of  the  water  blower,  if  power  is  at  hand,  as  is  usually 
the  case  in  most  mill  or  furnace  laboratories,  the  air  may  be  sup- 
plied by  a  small  Root  or  Crowell  positive  pressure  blower,  belted 
on  to  a  shaft,  in  some  convenient  place  about  the  mill.  These 
blowers  can  be  obtained  from  most  dealers  in  laboratory  supplies. 
Any  means  which  will  give  a  constant  supply  of  air,  at  an  unvary- 
ing pressure  of  about  one  pound  per  square  inch,  or  even  less,  will 
answer  the  purpose  of  an  air  pump  for  this  machine.  The  pres- 
sure of  course  must  be  low  or  the  burners  will  be  hard  to  light. 
Any  change  of  pressure  will  also  usually  result  in  the  flames 
dropping  or  being  blown  out. 

This  gas  machine  can  be  constructed  with  water  blower  for 
about  $25  or  with  the  Root  or  Crowell  blower  for  about  $40.00, 
depending  very  much  on  the  amount  of  piping  that  has  to  be 
done. 

Gasolene  for  these  machines  should  be  what  is  known  as  88° 


64  SMALL    CHEMICAL    LABORATORIES. 

and  should  be  purchased  if  possible  in  iron  drums.  A  spigot  may 
then  be  screwed  into  the  drum  and  the  latter  set  on  its  side,  or  a 
suitable  rest,  and  the  gasolene  drawn  as  required  for  replenishing 
the  generator.  The  gasolene  should  be  kept  in  a  small  shed,  away 
from  other  buildings. 


Fig.  41. — Simple  Gas  Machine. 

Acetylene, — Acetylene  gas  is  now  used  for  laboratory  pur- 
poses and  quite  a  number  of  firms  manufacture  generators  and 
burners  especially  suited  to  laboratory  requirements.  Acetylene 
gas  gives  off  great  heat  when  properly  burned,  but  it  requires 
special  pattern  Bunsens  and  stoves  to  burn  it  without  loss.  It  is 


HEATING  APPLIANCES. 


stated  by  one  chemist  who  uses  acetylene  that  it  does  not  cause 
the  deterioration  of  platinum  ware  which  other  forms  of  gas  do. 
It  compares  very  favorably  with  gasolene  gas  in  economy. 

Where  much  work  is  done  with  crucible  furnaces  and  high 
temperatures  are  needed,  acetylene  gas  may  be  the  best  gas  to 
install,  as  it  is  possible  with  it  to  produce  temperatures  higher 
than  those  obtainable  with  gasolene  gas  or  even  with  coal  gas. 

Burners. — Figures  42,  43  and  44  show  forms  of  burners  well 
suited  to  gasolene  gas.  The  author  has  always  found  the  form 
shown  in  Fig.  42  to  answer  very  well,  but  the  other  two  burners 
have  the  additional  advantage  that  they  do  not  light  back  and 
hence  are  safer. 

Where  burners  are  to  be  used  for  heating  dishes,  a  crown 


CANT 

LIGHT  BACK. 


Fig.  4l>. 


Fig.  43. 
Burners  for  Gasolene  Gas. 


Fig.  44. 


or  gauze  top  for  the  former  distributes  the  heat  more  uniformly. 
For  bending  glass  a  wing  top  is  needed.  Stars,  which  slip  over 
the  tube  of  the  burner  and  can  be  held  at  any  height,  are  used  to 
support  chimneys  of  glass,  sheet  iron,  or  best  mica.  These  chim- 
neys keep  the  flame  of  the  burner  from  being  blown  about 
by  every  draft.  Julian  has  devised  an  adjustable  support  for 
dishes,  platinum  triangles,  etc.,  which  can  be  slipped  over  the 
tube  of  the  burner  and  kept  at  any  height  by  a  thumbscrew.  This 
does  away  with  an  independent  support. 

Porcelain  burners  are  obtainable  for  use  in  hoods  and  other 
places  where  metal  burners  would  be  badly  corroded.  One  of  the 
neatest  forms  of  these  is  Chaddock's.  As  this  burner  is  provided 
with  a  chimney,  on  which  to  set  a  triangle,  and  a  support  for 
dishes,  etc.,  no  metal  tripod  or  retort  stand  has  to  be  used. 


66  SMALL    CHEMICAL    LABORATORIES. 

When  uniform  heat  is  desired,  as  in  evaporating  solutions, 
an  argand  burner  with  chimney  may  be  used.  If  ordinary  burn- 
ers are  used,  place  on  top  the  gauze  on  which  the  dish  is  sup- 
ported, a  round  piece  of  asbestos  paper  the  size  of  a  silver  dollar 
and  then  place  the  dish  on  top  of  this  and  the  burner  directly 
under  it.  This  spreads  the  heat,  and  the  evaporation  can  be 
made  to  proceed  evenly  without  ebullition.  Teclue  burners  are 
very  powerful  burners  and  are  usually  used  for  heating  large 
sand,  air  or  water-baths.  Burners  with  from  2  to  6  tubes,  either 
arranged  in  clusters  or  in  a  row,  are  also  used  for  the  same 
purpose. 

Stoves  and  Hot  Plates. — The  simplest  hot  plate  is  a  sheet  of 
boiler  plate,  %  to  *4  inch  thick,  resting  on  a  tripod  and  heated 
by  a  Bunsen  burner.  An  improvement  on  this  is  a  plate  resting 
on  a  Fletcher's  burner.  Since  cast  iron  does  not  warp  as  bad  as 
wrought  iron  a  stove  lid  makes  a  good  hot  plate  and  may  be 
used  where  only  a  little  work  is  done,  being  heated  by  a  Fletcher 
or  a  Teclue  burner.  Gas  stoves  may  be  procured  either  of  chemi- 
cal supply  houses  or  else  from  local  dealers  in  gas  fixtures.  The 
most  convenient  thing,  however,  is  the  regular  hot  plate  sold  by 
chemical  supply  houses  and  consisting  of  a  gas  stove  having  a 
polished  cast  steel  top.  The  burners  are  arranged  to  give  a  uni- 
form heat  and  they  may  be  lit  as  needed  so  as  to  have  one  part  of 
the  plate  hotter  than  the  other.  A  hot  plate  i4l/2  x  iSy2  inches 
arranged  for  gasolene  gas  may  be  procured  for  $12.00. 

Sand-baths  are  convenient  for  heating  dishes  and  other 
round-bottomed  utensils,  but  they  are  dirty  things  at  best  and  un- 
suited'  to  the  analytical  laboratory. 

Water-Baths  and  Air-Baths. — The  water-bath  is  much  used 
for  evaporations  and  is  made  of  both  enameled  ware  and  copper. 
They  may  be  purchased  with  any  number  of  holes,  which  are 
covered  by  concentric  rings  so  that  any  sized  dish  may  be  set  upon 
them.  They  may  be  heated  by  a  Bunsen  burner,  or,  if  steam  is 
run  into  the  laboratory,  they  may  be  attached  to  this.  Water- 
baths  are  also  obtainable  for  keeping  funnels  and  contents  hot 
during  filtering.  Water-baths  heated  over  a  burner  are  liable 
from  carelessness  to  boil  dry.  To  guard  against  this,  the  constant 
level  apparatus  is  used  in  some  laboratories.  This  is  shown  in 

.  45- 
The  bottle,  B,  is  filled  with  water  and  closed  with  a  single- 


HEATING  APPLIANCES. 


67 


hole  cork  having  in  it  a  piece  of  short  glass  tubing,  d.  This  is 
placed  in  the  cup,  c,  of  the  water-bath,  A.  When  the  water  in  A 
falls  below  the  end  of  the  tube,  d,  air  enters  the  bottle  and  allows 
a  corresponding  amount  of  water  to  flow  out.  As  soon  as  the 
water  in  the  cup  rises  above  the  end  of  the  tube,  no  more  water, 
of  course,  can  run  out  of  the  bottle.  This  is  a  clumsy  arrange- 
ment, however,  and  may  be  dispensed  with,  as  a  very  little  ex- 
perience teaches  the  chemist  how  much  water  he  will  require  in 
his  bath  to  run  it  the  time  he  needs  it. 

Air  baths  for  drying  materials  are  needed  in  all  laboratories, 
and  are  used  for  determining  moisture  in  samples  and  for  drying 
ores,  coal,  etc.,  etc.  They  usually  consist  of  a  copper  box  pro- 
vided with  a  hinged  door  in  front  and  holes  for  the  insertion  of  a 


Fig.  45.— Constant  Level  for  Water  Baths. 

thermometer  and  for  the  escape  of  water  vapors  in  its  top.  The 
bath  is  provided  with  a  false  bottom,  to  prevent  destruction  of 
the  real  ore  by  the  burner  flame.  The  bath  is  heated  by  a  Bunsen 
burner.  It  is  necessary  to  control  the  temperature  of  the  bath  by 
a  thermometer  inserted  through  a  cork  in  the  opening  at  the  top 
of  the  oven.  The  required  temperature  can  be  maintained  by  ad- 
justing the  stock  cock  of  the  gas  supply.  Gas  regulators  called 
"Thermostats"  can  be  purchased  from  dealers  in  chemists'  sup- 
plies, and,  while  they  are  liable  to  get  out  of  order  by  becoming 
clogged  up,  they  are  nevertheless  very  convenient  for  keeping  a 
constant  temperature.  As  any  checking  of  the  gas  supply  is  like- 
ly to  cause  a  gasolene  gas  burner  to  strike  back,  it  is  best,  where 
a  thermostat  is  used  with  this,  to  have  two  burners,  only  one  of 


68 


SMALL    CHEMICAL    LABORATORIES. 


which  is  controlled  by  the  thermostat.  The  other  burner  is  turned 
low  and  the  two  burners  are  tilted  so  their  tops  are  close  to- 
gether. If  the  burner  attached  to  the  thermostat  goes  out,  as  it 
probably  will  when  the  gas  supply  is  checked,  it  will  be  lit  by  the 
other  one. 

Figure  46  shows  a  home-made  thermostat.  A  piece  of  large 
bore  tubing  is  blown  into  a  small  bulb,  A,  at  one  end  and  then 
about  2  inches  from  this  bent  into  a  U,  B,  as  shown  in  the  cut. 
This  U  is  filled  with  mercury  nearly  up  to  the  bulb.  A  piece 


Fig.  46.— Thermostat. 


of  thin  tubing,  C,  having  a  small  opening  at  F  (not  necessary  if 
two  burners  are  used)  is  inserted  in  the  large  tube  and  the  open- 
ing between  the  two  stopped  by  a  piece  of  rubber  tubing,  D.  The 
tube,  C,  is  attached  by  rubber  tubing  to  the  burner  and  the  tube, 
E,  to  the  gas  supply.  The  joint,  at  G,  is  to  allow  the  apparatus 
to  be  inserted  in  the  opening  of  the  air-bath.  To  regulate,  run 
the  temperature  up  until  the  thermometer  reads  the  maximum 
desired,  then  push  the  tube,  C,  down  until  it  just  goes  below  the 
surface  of  the  mercury.  This  '"Thermostat"  is  very  delicate,  but 
the  rubber  ring,  D,  sticks  to  the  tubes  and  makes  it  hard  to  move 
the  inner  tube,  C,  up  and  down. 


CHAPTER  X. 


PREPARATION  OF  DISTILLED  WATER. 

Automatic  Stills. — For  the  preparation  of  distilled  water  in 
the  laboratories,  nothing  are  quite  so  handy  as  the  automatic 
laboratory  stills  sold  by  various  dealers  in  chemical  supplies.  One 
of  the  best  forms  of  these  is  the  Jewell  automatic  water  still,  an- 
other good  form  is  the  Rochlitz  automatic  water  still,  Fig.  47, 
made  for  The  Scientific  Shop,  324  Dearborn  Street,  Chicago. 
This  latter  form  the  author  has  in  his  laboratory  and  it  is  prob- 
ably necessary  to  operate  it  not  more  than  a  third  of  the  time  to 
supply  all  the  water  needed  for  the  analytical  work.  It  gives  the 


Fig.  47.— Rochlitz  Automatic 
Water  Still. 


Pig.  48.— Jewell  Automatic 
Water  Still. 


70  SMALL    CHEMICAL    LABORATORIES. 

purest  water  of  any  of  the  small  stills  which  we  have  examined. 
When  pushed  it  will  distill  at  the  rate  of  about  one  gallon  every 
two  hours.  Its  price  was  $15.00. 

The  Jewell  still,  Fig.  48,  is  made  in  a  number  of  sizes,  the 
smallest  costing  $12.00  and  having  a  capacity  of  y2  gallon  per 
hour  and  the  largest  costing  $60.00  with  a  capacity  of  il/2  gal- 
lons an  hour.  These  stills  are  all  meant  to  be  heated  by  gas, 
though  the  smaller  sizes  may  be  heated  by  a  gasolene  burner. 
The  Rochlitz  still  may  be  heated  over  a  small  oil  stove  as  it  differs 
somewhat  in  construction  from  the  Jewell  still. 

Condensing  Steam  from  Boilers,  Etc. — Other  forms  of  auto- 
matic water  stills  are  on  the  market  and  are  described  in  various 


—    •» 

J  j 

=^C 

'>?  /" 

I  i 

-T|--:^^ 

^=;&.  " 

I* 

d^-'^.''" 

—  * 

C 

1 

ftj 

1 

r 

i 

Fig.   49.— Condenser   and   Trap   for   Waste    Steam. 

dealers'  catalogues.  The  automatic  stills  are  so  cheap  that  it 
hardly  pays  to  get  a  copper  retort  and  tin  worm  to  distill  water. 
While  a  few  dollars  first  cost  may  be  saved  by  purchasing  these, 
the  extra  trouble  of  watching  the  latter,  in  order  to  prevent  its 
boiling  dry,  and  the  extra  amount  of  gas  required  to  do  the 
work,  negative  any  such  saving  in  a  few  weeks.  Steam  from  the 
heating  line  may  also  be  condensed  for  distilled  water.  In  this 
event  a  trap  should  be  interposed  between  the  steam  line  and  the 
block  tin  pipe  coil  in  order  to  catch  any  drip  from  the  iron  pipe. 
Figure  49  shows  an  arrangement  of  this  kind.  A  is  the  trap.  It 
is  a  small  drum  made  of  galvanized  iron,  planished  copper  or  iron 
pipe.  It  is  provided  with  a  drip  cock,  B,  and  a  small  siphon,  C, 


PREPARATION  OF  DISTILLED  WATER.  71 

which  will  automatically  draw  off  the  water  when  it  reaches  a 
certain  height.  D  is  the  worm.  It  should  be  made  of  block  tin 
pipe.  The  cooling  water  enters  at  E  and  leaves  at  F.  If  the 
steam  is  drawn  from  the  boilers  of  a  large  plant  it  is  apt  to  con- 
tain oil,  which  will  condense  with  the  water  and  the  latter  will 
appear  milky  and  smell  of  kerosene.  While  for  some  work  this 
may  not  be  objectionable,  still  such  distilled  water  makes  the 
beakers  greasy  and  the  burette  levels  hard  to  read,  so  that  it  is 
far  better  to  get  one  of  the  automatic  stills  either  heated  by  gas 
or  steam.  Where  gasoline  lamps  are  used  the  Rochlitz  still,  men- 


Fig.  50.— Still  to  be  Heated  by  Steam. 

tioned  before,  may  be  used  and  heated  by  a  coal  oil  stove,  if 
the  gasolene  lamps  are  troublesome  or  the  gas  supply  is  limited. 

Large  Stills. — When  large  volumes  of  water  are  needed  a 
large  size  Jewell  still  heated  by  live  steam  from  the  boilers  of  the 
plant  will  be  found  most  convenient  and  economical.  They  are 
made  in  sizes  ranging  in  capacity  from  3  to  30  gallons  per  hour 
and  hence  are  large  enough  to  meet  any  laboratory  demand.  The 
F.  J.  Stokes  Machine  Co.,  I7th  and  Cambria  Sts.,  Philadelphia, 
also  make  automatic  stills  of  great  capacity  and  efficiency  to  be 
heated  by  live  steam. 

A  retort  heated  by  steam,  such  as  is  shown  in  Fig.  50,  may 


72  SMALL    CHEMICAL    LABORATORIES. 

also  be  attached  to  the  condenser  illustrated  in  Fig.  49.  This  is 
made  of  copper  and  is  heated  by  means  of  a  coil  of  £4 -inch  copper 
pipe  coiled  around  the  inside  of  the  retort.  This  coil  is  connected 
with  the  steam  line.  The  steam  from  the  retort  passes  up  into 
the  dome  and  from  this  into  a  worm  through  a  block  tin  pipe.  As 
the  water  boils  away  from  the  retort  more  is  automatically  sup- 
plied through  the  siphon  tube  shown. 

Containers  for  Distilled  Water. — For  holding  distilled  water 
one  or  two-gallon  bottles  are.  best,  because  one  can  be  filling  while 
the  other  is  being  used,  etc.  Distilled  water  attacks  glass,  dissolv- 
ing silica,  so  that  it  should  not  be  kept  any  great  length  of  time. 
For  this  reason  it  is  best  to  get  a  still  which  without  pushing  will 
distill  a  day's  supply  of  water  in  a  morning,  and  have  freshly  dis- 
tilled water  on  hand  every  day,  using  one  day  the  water  prepared 
the  morning  before,  and  emptying  each  bottle  before  using  the 
next.  Tanks  lined  with  block  tin  are  used,  as  distilled  water  at- 
tacks tin  very  little.  They  should  be  soldered  with  pure  tin.  Car- 
boys, stone  jugs,  jars,  etc.,  of  large  capacities  should  not  be  used 
to  hold  distilled  water  in  laboratories  where  inorganic  gravimetric 
determinations  are  made,  as  water  kept  in  such  vessels  is  sure  to 
become  contaminated  with  silica,  etc.,  giving  high  results.  For 
the  same  reason  the  practice  of  using  large  stills  heated  by  coal 
fires  and  run  only  now  and  then,  long  enough  to  fill  up  tanks  or 
bottles  with  sufficient  water  to  supply  the  laboratory  for  a  month 
or  two,  is  decidedly  objectionable,  on  the  score  of  accuracy.  Dis- 
tilled water  should  be  occasionally  tested  for  contaminations  by 
evaporation  in  a  weighed  dish. 


CHAPTER  XL 
APPARATUS  FOR  ELECTROCHEMICAL  ANALYSIS.1 

Electrolytic  determinations  are  now  part  of  the  rou- 
tine of  many  commercial  laboratories  and  means  for  carrying 
out  such  work  will  usually  be  found  in  every  well-equipped  metal- 
lurgical laboratory,  no  matter  how  small  it  may  be.  In  determin- 
ing copper,  nickel,  bismuth,  etc.,  the  electrolytic  methods  are  far 
more  satisfactory  than  the  precipitation  or  volumetric  ones, 
hence  in  a  laboratory  where  ores  containing  copper  are  likely  to 
be  brought  for  analysis  or  where  bearing  metals  or  alloys,  nickel, 
steel,  etc.,  are  analyzed  means  should  be  provided  for  electrolytic 
work. 

Use  of  the  Electric  Lighting  Current. — Stillwell  and  Austin2 
were,  I  believe,  the  first  to  suggest  the  use  of  the  electric  light  cur- 
rent for  the  determination  of  metals  in  the  electrolytic  way,  and  the 
writer  has  found  this  to  be  not  only  sufficient  for  ordinary  tech- 
nical purposes,  but  also  by  far  the  most  convenient.  When  avail- 
able, it  is  much  cheaper  than  batteries  and  saves  the  operator 
much  trouble.  The  only  disadvantage  in  connection  with  its  use 
is  the  constant  voltage  which  is  usually  no  or  220.  Indirect 
or  alternating  currents  must  of  course  be  transformed  to  direct 
currents.  This  necessitates  the  use  of  a  transformer,  which  may 
make  the  cost  of  installation  of  the  outfit  for  electrolytic  work  so 
great  as  to  make  the  use  of  batteries  preferable  to  that  of  the 
electric  light  current. 

It  is  of  course  necessary  to  reduce  the  strength  of  the  cur- 
rent. For  this  purpose  the  resistance  board  shown  in  Fig.  51  and 
designed  by  the  author  is  convenient  and  satisfactory.  It  consists 
of  a  stout  board,  2  inches  thick  and  24  inches  by  8  inches.  This 
board  should  have  its  top  covered  by  a  piece  of  asbestos  board,  to 
guard  against  fire,  etc.,  so  that  the  apparatus  may  be  left  over 
night  without  danger.  In  a  line  down  the  middle  of  this  board, 

*Part  of  the  material   in  this  chapter  is  taken  from   articles     by     Dr.     W.     H. 
Easton  in  the  Chemical  Engineer,  April  and  September,   1905. 
2Jour.  Anal,  and  App.   Chem.,   VI.,   129. 


5*v 

/  OF  THE  X 

>  I        .       * 


74 


SMALL    CHEMICAL    LABORATORIES. 


with  their  centres  3  inches  apart,  seven  porcelain  keyless  sockets 
or  receptacles,  blt  bz,  bz,  etc.,  should  be  fastened.  The  best  form 
of  receptacle  to  use  is  that  shown  in  the  cut.  Single  pole  knife 
switches,  alf  az,  a3)  etc.,  are  also  placed  three  on  each  side,  as 
shown  in  Fig.  51.  At  either  end  of  the  board  a  binding  post  d* 
and  d2  is  placed.  Each  receptacle  is  connected  to  the  next  recep- 
tacle and  also  to  one  point  of  the  switch,  by  means  of  short  pieces 
of  insulated  copper  wire.  The  end  receptacles  are  also  connected, 
each  to  a  binding  post.  All  the  connections  should  be  made  as 
shown. 

With  this  board  should  also  be  provided  six  i6-candle  power 


Fig.  51.— Lamp  Resistance  for  Electrochemical  Work. 

lamps,  six  32-candle  power  lamps,  six  5O-candle  power  lamps,  and 
a  safety  plug  of  say  10  amperes.  To  use  the  board,  connect  one  of 
the  binding  posts  to  one  terminal  of  the  electric  light  current  and 
connect  the  other  with  one  of  the  electrodes  of  the  solution  to  be 
electrolyzed.  Now,  if  a  weak  current  is  desired,  screw  i6-candle 
power  lamps  into  the  sockets  and  open  all  the  switches.  The 
current  will  then  travel  through  all  seven  of  the  lamps,  as  follows : 
— from  d2  through  the  lamp  clt  and  from  this  to  the  lamp  c2,  by 
means  of  the  wire  eif  and  thence  to  the  binding  post  d1  through 
e*,  cz,  e3,  Ct,  e±,  c5)  e5)  CQ,  eQ,  cn,  in  order.  For  a  resistance  of  six 
lamps,  remove  the  lamp  c7  and  place  the  safety  plug  in  the  recep- 


ELECTROLYTIC  ANALYSIS.  75 

tacle  &7.  For  five  lamps,  close  the  switch  ac ;  for  four  lamps,  the 
switch  a5 ;  for  three  lamps,  a4 ;  for  two  lamps,  a3  and  for  one 
lamp,  a2. 

For  stronger  currents  the  lamps  may  be  put  in  parallel.  To 
do  this,  take  out  the  safety  plug  from  b-,  close  all  the  switches  and 
put  in  from  one  to  seven  lamps,  according  to  the  strength  current 
desired.  Seven  lamps  will  give  about  3.5  amperes,  while  two 
lamps  will  give  about  one  ampere.  For  yet  stronger  currents  put 
in  the  32-candle  power  or  the  5O-candle  power  lamps.  For  very 
weak  currents,  use  another  board  and  shunt  the  current  through 
this  around  a  light.  For  analytical  work,  however,  the  above 
board  is  sufficient  and  only  i6-candle  power  lamps  need  be  used, 
unless  the  rotating  anode  is  to  be  employed,  when  5<D-candle 
power  lamps  will  be  needed,  since  the  currents  for  this  work  are 
much  stronger. 

The  above  board  provided  with  i6-candle  power  and  5O-candle 
power  lamps  will  give  a  range  of  current  of  from  about  0.07  am- 
pere to  about  n.o  amperes.  The  resistance  of  the  board  can  be 
calculated,  sufficiently  near  the  truth  for  analytical  purposes,  by 
assuming  for  a  no  volt  circuit,  that  the  i6-candle  power  lamps 
have  a  resistance  of  220  ohms;  the  32-candle  power  lamps,  108 
ohms;  and  the  so-candle  power  lamps,  69  ohms.  If,  therefore, 
seven  16  C.  P.  lamps  are  in  series,  according  to  Ohm's  law : 

volts  no  i 

Amperes  = or  Amperes  —  =  — . 

ohms  220  x  7          14 

Or  the  resistance  of  the  lamps  is  1/14  ampere  or  0.07  ampere.  If 
now  the  seven  16  C.  P.  lamps  are  in  parallel  the  resistance  will  be 

no 

x  7  or  3.5  amperes. 

220 

Instead  of  calculating  the  resistance  of  the  board,  it  is  pre- 
ferable to  determine  it  by  means  of  an  ammeter.  This  may  be 
done  once  for  all,  and  the  values  for  each  combination  of  lights 
recorded  in  a  note  book,  or  the  measuring  instrument  may  be 
introduced  into  the  circuit  while  the  determinations  are  being 
made.  This  latter  plan  is  preferable,  but  necessitates  the  pos- 
session of  an  ammeter  by  the  laboratory,  while  in  the  former 
event,  the  work  of  determining  the  resistance  may  be  done  in 
some  electric  light  station,  or  by  some  friendly  electrician. 


76  SMALL    CHEMICAL    LABORATORIES. 

To  start  with  a  low  resistance  and  increase  to  a  greater,  place 
all  seven  lamps  in  the  board  and  open  all  the  switches  and  con- 
nect up  the  apparatus  with  the  terminal  wires.  Now  take  out  the 
lamp  c7  and  screw  the  safety  plug  in  the  receptacle  b7.  Then 
close  in  turn  the  switches  ae,  a5,  a4,  as,  and  a2.  Do  not  close  the 
switch  aif  however,  or  short  circuiting  will  take  place.  Now  take 
out  the  plug  from  the  receptacle  b7  and  unscrew  all  the  lamps, 
except  Ci,  from  the  receptacles,  far  enough  to  break  the  contact. 
Close  the  switch  ax  and  screw  in  the  lamps  to  make  contact  one 
by  one. 

To  avoid  short  circuiting,  the  connection  between  &t  and  dz 
or  between  b7  and  d±  should  be  made  with  fuse  wire,  or  another 
lamp  receptacle  may  be  put  in  between  the  receptacle  b7  and  the 
binding  post  dlt  connected  to  b7  and  d^  by  pieces  of  wire,  and  a 
safety  plug  kept  in  this  all  the  time. 

The  board  may  be  fastened  to  the  wall,  or  a  cord  and  plug 
socket  may  be  fastened  to  it  so  that  it  can  be  put  away  in  a  desk 
when  not  in  use.  When  wanted  the  board  can  be  readily  at- 
tached to  the  current  by  screwing  the  plug  socket  into  a  lamp 
receptacle,  on  the  wall  or  hanging  from  the  ceiling. 

Gravity  Cells. — When  the  electric  lighting  current  is  not  at 
hand,  batteries  must,  of  course,  be  used.  For  ordinary  analytical 
work  six  crowfoot  or  gravity  cells  will  be  found  sufficient  and 
these  can  be  arranged  in  series  or  in  parallel  as  the  case  may  re- 
quire. No  resistance  board  is  needed,  as  the  strength  of  the  cur- 
rent can  be  controlled  by  the  number  and  the  arrangement  of 
the  cells  themselves.  Where  currents  of  greater  strength  than 
one  or  two  amperes  are  needed  the  bichromate  cell  should  be  used 
in  place  of  the  gravity  cells.  When  weak  currents  are  to  be  used, 
however,  nothing  will  be  found  so  easy  to  take  care  of  as  the 
crowfoot  or  gravity  cells.  These  may  be  arranged  in  a  closet 
under  the  work-table  on  which  the  electrolytic  work  is  done. 
They  should  be  connected  up  to  a  board  as  shown  in  Fig.  52,  so 
that  they  can  be  readily  arranged  in  any  way  desired. 

This  board  consists  of  two  narrow  strips  of  copper  or  brass, 
E  and  D,  running  along  the  front  edge  or  on  the  side  of  the  work- 
bench just  under  the  top.  These  strips  should  have  a  binding 
post  at  either  end  of  which  the  wires  leading  to  the  anode  and 
cathode  of  the  solution  to  be  electrolyzed  should  be  connected, 
and  should  be  about  6  inches  apart.  Equidistant  between  the  two 


ELECTROLYTIC  ANALYSIS.  77 

strips  of  metal  twelve  short  pieces  of  brass  spring  alt  blt  a2,  b2, 
etc.,  should  be  screwed  into  the  board.  These  springs  should  be 
about  3^  inches  long  and  should  reach  to  either  the  strip  D  or  E. 
Each  pair  of  springs  should  be  placed  so  that  the  adjacent  spring 
of  the  following  pair  can  rest  on  the  screw  holding  the  spring 
itself  to  the  board.  That  is,  referring  to  Fig.  52,  the  spring  a2 
should  be  so  placed  that  it  can  be  swung  around  so  as  to  rest  on 
either  the  copper  strips  E  or  D  or  on  the  screw  holding  the  spring 
b-L  to  the  board.  Each  spring  should  be  connected  to  a  pole  of  a 


Fig.  52. — Board  to  Facilitate  the  Arrangement  of  Batteries. 

battery.  The  springs  alf  a2,  a3,  etc.,  should  be  connected  to  the 
zincs  of  the  cells,  and  the  springs  blt  b2,  &3,  etc.,  should  be  con- 
nected to  the  coppers  of  the  cells.  Fig.  53  shows  an  elevation  of 
one  of  the  springs.  A  is  a  piece  of  brass  spring  with  a  round 
hole  bored  in  one  end  and  the  other  turned  up  to  form  a  handle. 
This  spring  is  fastened  to  the  table  by  means  of  the  brass  screw 
B,  and  should  be  held  in  place  by  two  washers,  as  shown.  C  is  a 
piece  of  copper  wire  connecting  the  spring  with  the  battery.  D 
is  the  long  copper  strip  running  the  length  of  the  table. 


Fig.    53. — Spring   Connector  for   Battery   Board. 

With  the  springs  in  the  position  shown  in  Fig.  52,  the  six 
cells  are  in  series.  The  spring  al  connected  with  the  zinc  of  cell 
cx  rests  on  the  strip  D,  and  the  spring  b*  connected  with  the  cop- 
per element  of  cell  cti  rests  on  the  strip  E,  while  the  copper  ele- 
ments of  the  cells  clf  c2,  c3,  c4,  and  c5  are  connected  to  the  zinc 
elements  of  the  next  cell  by  means  of  the  springs  a2,  a3,  a4,  a5  and 
ae.  The  springs  blt  b2,  bz,  b4  and  £?5  are  out  of  service  and  rest 
merely  on  the  wood. 

To  connect  in  parallel,  the  springs  marked  alf  a2,  03,  a4,  as 


78  SMALL    CHEMICAL    LABORATORIES. 

and  a6  should  rest  on  the  strip  D  and  those  marked  blt  b2,  b3,  b±,  b5 
and  bQ  should  rest  on  the  strip  E. 

A  battery  of  six  crowfoot  cells  can  be  bought  for  less  than 
$5-00- 

Storage  Batteries. — Storage  batteries  are  a  very  convenient 
source  of  current  when  means  for  charging  them  is  at  hand  and  a 
board  like  that  described  above  will  be  found  very  handy  for  con- 
necting them  up.  Their  relatively  high  voltage  and  amperage 
make  them  more  suitable  than  any  other  form  of  battery,  while 
their  discharge  is  very  steady  and  dependable.  They  give  a  volt- 
age of  about  two.  A  higher  voltage  is  obtained  by  adding  more 
cells  in  series,  (i.  e.,  the  positive  pole  of  one  to  the  negative  pole 
of  the  next,  and  so  on). 

Cells  can  be  obtained  for  any  amperage  capacity,  the  amper- 
age required  to  exhaust  the  cell  in  eight  hours  being  the  standard. 
A  cell  of  two  and  a  half  amperes  for  eight  hours  discharge  is 
large  enough  for  ordinary  use,  although  it  is  convenient  to  have 
cells  of  a  larger  capacity  so  as  to  allow  longer  intervals  between 
charges. 

Unfortunately,  storage  batteries  cannot  be  used  unless  there 
is  some  means  at  hand  for  charging  them,  and  moreover  they  are 
very  delicate  and  need  careful  attention  to  prevent  them  from 
being  ruined.  Explicit  directions  accompany  the  batteries,  and 
if  means  for  charging  them,  such  as  the  lighting  circuit  and  a 
rheostat  sufficient  to  reduce  the  current  to  the  normal  charging 
rate,  are  at  hand,  nothing  better  for  electrolysis  can  be  obtained. 

A  description  of  storage  batteries,  their  use  and  care  is  be- 
yond the  range  and  scope  of  this  paper;  an  excellent  chapter  on 
storage  batteries,  written  by  Prof.  F.  B.  Crocker,  will,  however, 
be  found  in  a  little  book,  "Practical  Lessons  in  Electricity,"  pub- 
lished by  The  American  School  of  Correspondence  at  Armour 
Institute  of  Technology,  Chicago,  111.,  which  anyone  interested 
in  the  subject  of  electrochemistry  will  do  well  to  procure. 

Rheostat. — Where  batteries  or  storage  cells  are  used  some 
means  other  than  the  lamp  board  previously  described  must  be 
provided,  since  the  resistance  of  this  is  far  too  great  for  such 
sources  of  current.  Rheostats  are  manufactured  for  this  pur- 
pose, made  up  with  coils  of  resistance  wire,  and  a  movable  arm 
that  can  be  placed  so  as  to  allow  the  current  to  pass  through  as 
much  of  the  resistance  as  desired.  Such  rheostats  are  best  pur- 


ELECTROLYTIC  ANALYSIS.  79 

chased.  They  should  be  constructed  so  that  they  will  cut  down 
the  current  from  one  cell,  from  full  strength  to  about  .105  ampere, 
in  from  ten  to  twenty  equal  steps;  and  be  able  to  withstand  the 
full  current  from  all  the  batteries  at  once. 

A  water  rheostat  makes  a  very  cheap  and  simple  means  of 
controlling  the  current.  A  glass  or  earthenware  jar  of  about 
three  quarts  capacity  is  filled  with  a  very  weak  solution  of  sul- 
phuric acid.  Two  arc  lamp  carbons  are  attached  to  the  terminals 
of  the  current  in  series  and  dip  into  the  solution.  The  farther 
the  carbons  are  apart  the  greater  the  resistance.  By  fastening 
one  on  the  edge  of  the  jar  and  hanging  the  other  on  the  edge  with 
a  clip  so  that  it  may  be  placed  anywhere,  an  excellent  rheostat  is 
obtained.  The  resistance  in  the  solution  can  be  decreased  by 


/••H 


H 

Fig.  54.— Diagram  Showing  Arrangement  of  Cells  in  Series  Parallel. 


Fig.  55.— Diagram  Showing  Arrangement  of  Cells  in  Parallel. 

adding  acid,  and  increased  by  adding  water.  The  size  of  the  jar, 
etc.,  will  depend  upon  the  conditions  of  the  circuit,  and  are  easily 
found  by  experiment. 

Arrangement  of  Cells. — The  diagrams  show  how  certain 
results  can  be  obtained  by  altering  the  arrangements  of  the  con- 
nections. It  must  be  noted  that  a  voltage  of  above  the  desired 
figure  must  be  obtained  by  adding  batteries  in  series  and  then 
cutting  down  to  the  right  point  by  the  rheostat.  As  mentioned 
before,  by  the  series  arrangement,  the  cells  add  their  voltage  to 
the  circuit,  but  the  amperage  remains  about  the  same  as  for  one 
cell.  Fig.  54  represents  the  series  arrangement,  in  which  the 
short  thick  lines  represent  the  zincs  and  the  long  thin  lines  the 
coppers.  The  irregular  lines  represent  connecting  wires.  If  3Va 


80  SMALL    CHEMICAL    LABORATORIES. 

volts  are  desired,  the  voltage  is  brought  up  to  four  by  adding  four 
cells,  and  then  reducing  the  voltage  to  3^  by  the  rheostat.  This 
arrangement  will  give  an  amperage  depending  upon  the  resistance 
in  the  circuit  and  electrolyte.  It  should  in  most  cases  be  suffi- 
cient, since  the  current  usually  required  is  very  small,  but  if  it  is 
not,  the  amperage  can  be  doubled  by  adding  an  equal  number  of 
cells  in  parallel.  Fig.  55  represents  this  arrangement.  This  is 
a  series  parallel  arrangement,  giving  the  same  voltage  as  in  Fig. 
54,  but  twice  the  amperage.  It  will  be  noticed  that  there  are 
four  groups  of  cells.  In  each  group  there  are  two  cells  with  the 
zinc  connected  to  zinc  and  the  copper  to  copper.  But  the  zincs 
of  one  group  are  connected  to  the  coppers  of  the  next,  and  so  on. 
In  making  these  arrangements,  the  same  proportions  always  hold 
true,  so  that  any  combination  of  cells,  to  give  almost  any  current, 
can  be  obtained. 


Fig.  56.— Platinum  Spiral  Anode. 

Electrodes. — In  electrochemical  analysis,  a  platinum  wire  or 
spiral  is  usually  used  as  an  anode,  Fig.  56,  and  a  platinum  dish, 
cone  or  cylinder  for  the  cathode.  When  the  deposit  to  be  weighed 
is  formed  on  the  anode  the  cone  or  dish  is  used  as  the  anode,  and 
the  spiral  for  the  cathode.  Aluminum  cathodes  have  been  pro- 
posed for  copper  analysis,  and  even  copper  ones  would  probably 
give  satisfactory  results  in  this  case.  When  obtainable,  however, 
platinum  should  be  used. 

The  most  satisfactory  cathode  is  a  small  platinum  dish 
weighing  about  30  to  50  grams.  When  large  volumes  of  solu- 
tions have  to  be  electrolyzed  the  cone  or  cylinder  must  of  course 
be  used  and  the  solution  held  in  a  beaker. 

Stands. — Figure  57  shows  a  convenient  stand  for  use  when 
a  platinum  dish  is  employed  as  a  cathode.  It  consists  of  a  wooden 
block,  A,  about  2  inches  thick  and  4  or  5  inches  square,  depend- 


ELECTROLYTIC  ANALYSIS. 


81 


ing  on  the  size  of  the  dish.  A  round  hole  about  an  inch  deep 
and  about  3  inches  in  diameter  should  be  gouged  out  of  this  and 
a  triangle,  C,  of  copper  wire  fastened  above  this,  as  shown  in  the 
illustration,  by  two  round-headed  screws  ft  and  /2,  and  a  binding 
post,  e.  A  light  wooden  frame,  B,  should  be  fastened  to  the  block, 
A,  and  the  binding  post,  d,  screwed  midway  in  the  top  piece  of 
this.  The  binding  post,  d,  should  be  for  two  wires  and  the  second 

if 


V  "&  NJ 

A     c     A 


Fig.   57.— Compact  and  Simple  Stand  for  Electrochemical  Analysis. 

hole  should  be  directly  over  the  centre  of  the  triangle.  The  dish 
to  be  used  as  a  cathode  should  rest  on  the  wire  triangle  and  the 
platinum  wire  to  be  used  for  an  anode  should  pass  through  one 
hole  of  the  binding  post  d.  The  wires  carrying  the  current  can 
then  be  attached  one  (+)  at  the  vacant  hole  of  the  binding  post  d 
and  the  other  ( — )  at  the  binding  post  e.  When  a  cone  or  a 
cylinder  is  used  as  a  cathode,  the  block,  A,  should  be  made  solid, 
without  the  hole,  and  the  frame  should  be  high  enough  to  permit 


82 


SMALL    CHEMICAL    LABORATORIES. 


a  beaker  to  be  moved  in  and  out  under  it  comfortably.  Another 
binding  post  similar  to  d  should  then  be  fastened  beside  d  to  hold 
the  cone. 

Very  often  supports  similar  to  retort  stands,  except  that  the 
supporting  rod  must  be  of  heavy  glass  to  avoid  short  circuits,  are 


J 


Fig.   58. — Support  for  Electrochemical  Analysis. 

used.  Figure  58  shows  such  a  stand.  The  supporting  arms  or 
rings  can  be  obtained  with  binding  posts  to  receive  the  terminals, 
and  must  be  of  bright  metal,  not  painted.  If  the  platinum  dish 
is  used  it  sets  directly  upon  a  ring  clamped  to  the  glass  supporting 


Fig.  59.— Ammeter— Weston. 

rod.  It  is  preferable  to  provide  this  ring  with  three  platinum 
points  for  contact  with  the  dish.  If  the  dish  is  to  be  heated,  a 
sheet  of  asbestos  is  fastened  on  the  under  side  of  the  ring  in  order 
that  heat  may  be  applied  to  the  solution  without  the  dish  coming 
in  contact  with  the  bare  flame. 


ELECTROLYTIC  ANALYSIS.  83 

Measuring  Instruments. — For  measuring  the  current  there 
will  be  needed  an  ammeter  and  a  voltmeter. 

The  Ammeter,  Fig.  59,  measures  the  amperage  or  amount  of 
current.  The  instrument  should  read  from  1/100  of  an  ampere  to 
at  least  two.  It  is  connected  with  the  circuit  in  series,  as  in 
Fig.  61. 


Fig.  GO. — Voltmeter— Weston. 

The  Voltmeter,  Fig.  60,  registers  the  volts  or  force  of  the 
current.  It  should  read  from  y±  to  10  volts.  It  is  placed  as 
mentioned  before  in  parallel,  and  between  the  precipitating  vessel 
and  all  other  parts  of  the  circuit. 


Fig.  61. — Assembling  the  Circuit  Where  Current  is  to  be  Measured. 

Where  the  current  is  to  be  measured,  the  proper  method  of 
assembling  the  circuit  is  shown  in  Fig.  61.  It  will  be  noted  that 
the  rheostat  and  ammeter  are  in  series  and  the  voltmeter  in 
parallel.  There  must  be  no  other  instrument  between  the  volt- 
meter and  the  precipitating  dish,  as  the  true  voltage  between  the 
anode  and  cathode  will  be  given  by  this  position  only. 


84  SMALL    CHEMICAL    LABORATORIES. 

Rotating  Anode. — Many  electrochemical  determinations  can 
have  the  time  necessary  for  complete  deposition  of  the  metal 
greatly  shortened  by  rotating  the  anode.  Means  for  doing  this 
are  described  below.  For  the  cathode  a  platinum  dish  is  best 
suited. 

The  anode  used  is  a  spiral  about  two  inches  in  diameter, 
made  of  heavy  platinum  wire.  It  is  made  slightly  bowl-shaped 
so  that  it  will  remain  immersed  in  the  liquid  in  spite  of  the  funnel- 
shaped  form  assumed  by  the  latter  on  rotating  the  anode.  Figure 
62  shows  its  construction. 


Fig.   62.— Rotating  Anode. 

Any  suitable  means  for  revolving  the  anode  may  be  used 
providing  the  rotations  per  minute  are  high  enough.  A  water 
motor,  electric  motor,  or  even  power  derived  from  shafting  will 
answer.  But  undoubtedly  an  electric  motor  run  by  the  lighting 
circuit  is  the  most  convenient.  The  anode  is  driven  by  a  small 
round  belt,  and  the  use  of  cone  or  stepped  pulleys  will  be  found 
convenient,  as  several  speeds  can  be  gotten  in  this  way.  Figure 
63  shows  the  general  arrangement. 

The  anode  should  revolve  at  about  700  revolutions  per 
minute. 


ELECTROLYTIC  ANALYSIS. 


Pulley 


Jtotor 

Connections 


Fig.   63. — Apparatus   for  Electrochemical  Analysis  by  Means  of  Rotating 

Anode. 

When  many  determinations  have  to  be  made  at  the  same 
time,  one  motor  may  of  course  be  made  to  do  for  all  by  crossing 
the  belt  after  each  pulley.  In  this  case  the  mortar  and  bearings 
of  the  anodes  should  all  be  mounted  on  the  same  framework. 


CHAPTER  XII. 
SAMPLING  APPLIANCES. 

The  apparatus  used  to  reduce  samples  of  ore,  rock,  coal, 
minerals,  etc.  from  the  dimensions  usually  encountered  as  they 
are  brought  to  the  laboratory,  to  the  fine  powder  necessary  for 
the  analysis,  may  be  divided  into  two  classes,  (i)  crushers  and 
(2)  pulverizers.  The  former  are  used  simply  to  prepare  the 
material  for  the  latter.  Sometimes  a  pulverizer  may  be  used  also 
as  a  crusher.  The  ordinary  iron  mortar  is  an  example  of  this,  as 
it  may  be  used  not  only  to  break  down  the  large  pieces  of  material 
to  smaller  sizes,  but  also  to  reduce  these  latter  to  a  fine  powder. 
Where  small  samples,  of  say  from  one  to  five  pounds,  alone  are 
met  with,  the  iron  mortar  will  answer  this  purpose  fairly  well, 
particularly  if  much  of  this  work  does  not  have  to  be  done,  and 
in  many  small  laboratories  the  small  boy  and  the  iron  mortar  will 
be  found  an  excellent  combination  for  preparing  samples  for 
analysis. 

Mortar  and  Pestle. — Iron  mortars  can  be  obtained  in  a  va- 
riety of  shapes  and  sizes.  Usually  for  this  work,  however,  two 
mortars  will  be  found  handy,  one  of  about  a  quart  capacity  and 
one  holding  about  2  gallons.  These  mortars  should  have  their 
inside  surfaces  chilled.  This  will  make  the  wearing  surface  of 
the  mortar  hard,  while  the  iron  itself  will  be  tough  enough  to 
withstand  the  blows  of  the  pestle.  If  the  mortar  and  pestle  are 
made  of  steel,  they  should  be  tempered,  and  the  temper  drawn 
from  the  outside  of  the  mortar,  leaving  the  latter  tough. 

In  pulverizing  very  hard  ores,  the  wear  and  tear  on  the  pestle 
and  mortar  is  often  enough  to  contaminate  the  sample,  to  an 
appreciable  degree,  with  splinters,  etc.,  of  iron.  If  the  material 
to  be  powdered  is  neither  magnetic  nor  contains  magnetic  sub- 
stances, the  iron  entering  the  sample  from  the  mortar  and  pestle 
may  be  removed  by  the  use  of  a  magnet.  For  pulverizing  sam- 
ples of  Spiegel  or  white  iron,  mortars  of  high  carbon  steel,  prop- 
erly tempered  and  toughened  as  mentioned  above,  should  be  used. 


SAMPLING  APPLIANCES.  87 

These  can  be  procured  from  dealers  in  chemical  supplies,  and  are 
also  useful  for  pulverizing  very  hard  ores. 

Mortars  having  handles,  or  trunnions,  projecting  from  each 
side  to  facilitate  lifting  and  emptying  are  also  for  sale.  Very 
heavy  iron  mortars  may  be  attached  to  a  block  and  tackle,  so  that 
the  mortar  can  be  lifted  and  emptied  conveniently.  The  attach- 
ment can  usually  be  most  conveniently  made  by  means  of  a 
wrought  iron  band  or  collar  clamping  around  the  upper  part  of 
the  mortar  and  having  a  ring  welded  to  it,  through  which  the 
tackle  may  be  run. 

Mortars  can  best  be  set  upon  large  blocks  of  wood  while 
the  pounding  is  going  on.  In  order  to  keep  the  pieces  of  material 
from  flying  out  from  under  the  pestle  and  escaping  from  the  mor- 
tar, the  latter  should  be  covered  with  a  large  piece  of  leather,  hav- 
ing a  hole  cut  through  the  middle  for  the  pestle  to  pass  through. 
Mortars  can  usually  be  cleaned  by  merely  brushing  out  well  with 
a  stiff  bristle  paint  brush.  When  material  clings  to  the  side,  how- 
ever, this  can  be  removed  by  triturating  a  little  clean  dry  sand  in 
the  mortar  and  then  brushing  this  latter  out. 

Reducing  the  Bulk  of  Samples. — In  preparing  large  samples 
for  the  laboratory,  it  is  usual  to  crush  the  material  by  degrees, 
reducing  the  bulk  of  the  sample  after  each  crushing.  For  ex- 
ample, suppose  a  sample  of  twenty  pounds  of  limestone  is  brought 
to  the  laboratory,  consisting  mostly  of  pieces  of  stone  as  large  as 
a  hen's  egg  and  under.  The  whole  sample  is  first  crushed  to  a 
size  of  about  one-half  inch  particles,  and  this  is  then  reduced  to 
one-fourth  its  bulk  by  "quartering,"  and  the  portion  retained, 
about  5  pounds,  is  reduced  to  pieces  the  size  of  a  pea  and  smaller. 
The  sample  of  this  size  is  again  "quartered,"  and  the  remaining 
sample,  about  20  ozs.,  is  crushed  so  that  it  will  pass  a  20  mesh 
sieve  and  from  this  coarsely  ground  powder  about  I  or  2  ozs.  is 
selected  and  powdered  so  fine  that  it  will  all  pass  a  sieve  of  100 
meshes  to  the  linear  inch.  For  limestone,  this  would  be  fine 
enough,  but  for  refractory  ores  and  silicates,  it  would  be  neces- 
sary to  select  enough  of  this  material  (passing  the  No.  100  sieve) 
for  the  analysis,  and  pulverize  so  fine  that  no  grit  could  be  de- 
tected on  rubbing  over  the  back  of  the  hand  or  biting  between 
the  teeth. 

The  size  to  which  the  sample  should  be  crushed  before  re- 
ducing its  bulk    is  usually  determined  by  the  nature  of  the  ma- 


88  SMALL    CHEMICAL    LABORATORIES. 

terial.  When  a  sample  of  several  pounds  is  received  at  the  lab- 
oratory, if  the  material  appears  to  be  homogeneous  to  the  eye,  it 
will  be  sufficient  to  reduce  it  to  a  size  passing  a  half  inch  screen. 
If  the  material  is  not  of  a  homogeneous  nature  but  is  streaked 
with  bands  or  shot  with  pebbles  of  various  other  materials  the 
crushing  should  be  much  finer — unless  the  sample  is  a  very  large 
one,  say  10  Ibs.  or  more.  Judgment  is  required  in  preparing 
samples,  and  the  amount  of  work  to  be  done  can  often  be  greatly 
abridged  by  a  careful  study  of  the  material.  The  object  in  all 
cases  is  to  have  the  small  sample  of  one  gram,  or  even  less, 
weighed  out  on  the  balance  pan,  representative  of  the  large  one. 
Whether  it  is  or  not  can  usually  be  checked  in  a  simple  manner, 
by  preparing  two  small  samples  from  the  original  sample.  That 
is  when  the  first  "quartering"  is  done,  select  two  quarters  and 
treat  each  as  if  it  were  a  different  sample.  If  the  preparation  of 
the  sample  has  been  properly  done,  analytical  results  upon  the  two 
will  check.  However,  it  is  not  usually  with  the  laboratory  part 
of  the  work  of  sampling  that  fault  can  be  found,  but  rather  with 
the  field  work.  This  can  also  be  checked  by  taking  two  samples 
of  the  same  pile  or  car  of  ore,  coal,  etc.,  or  from  the  same  deposit 
of  limestone,  clay,  etc. 

For  determining  the  degree  of  crushing  to  be  done,  sieves  are 
most  convenient,  the  material  being  made  to  pass  each  sieve  in 
turn.  A  convenient  way  is  to  make  a  sample  of  5  Ibs.  or  more  all 
pass  a  one-half  inch  sieve.  This  sieve  can  be  made  of  ordinary 
galvanized  wire  screening,  having  meshes  y2  inch  square,  by  tack- 
ing on  to  a  wooden  frame  18  inches  square.  The  sieving  may  be 
done  over  paper  or  a  sheet  of  light  oil  cloth.  It  can  best  be  done, 
however,  over  a  zinc  or  galvanized  iron  pan,  30  inches  square  and 
having  a  wall,  2  inches  high,  running  around  it,  except  for  one 
corner,  which  is  left  open,  in  order  that  the  pan  may  be  conven- 
iently emptied.  The  sample  passing  a  y2  inch  screen  is  then 
"quartered"  and  the  quarter  selected  is  made  to  all  pass  a  screen 
having  meshes  J4  mcn  square,  or  16  to  the  square  inch.  This 
sample  is  now  quartered  or,  if  still  very  large  and  the  material  is 
homogeneous  enough  to  admit  of  it,  its  bulk  is  reduced  to  about 
one  pound  and  all  of  this  is  made  to  pass  a  sieve  having  20  meshes 
to  the  linear  inch.  This  sieve  can  be  bought,  and  is  what  is  known 
as  a  No.  20  sieve.  The  sample  passing  this  sieve  can  then  be  re- 
duced to  one-quarter  or  even  one-eighth  its  bulk  and  made  to  pass 


SAMPLING   APPLIANCES.  89 

a  sieve  having  100  meshes  to  the  linear  inch  (known  as  a  No.  100 
sieve).  If  further  grinding  is  necessary,  in  order  to  allow  the 
acids,  etc.,  to  act  on  the  powdered  material,  the  sample  is  spread 
out  on  a  clean  piece  of  paper  or  oil  cloth,  divided  into  a  number  of 
squares  and  as  much  of  the  material  as  will  be  needed  for  the 
analyses  is  taken  by  removing,  from  each  square,  a  little  of  the 
material,  on  the  point  of  a  spatula.  This  material  is  then  placed 
in  an  agate  mortar  and  very  finely  pulverized. 

The  operation  of  reducing  the  bulk  of  a  sample  is  usually 
known  as  "quartering"  and  is  conducted  in  the  following  man- 
ner :  The  sample  is  poured  upon  a  piece  of  clean,  tough  paper 
or  oil  cloth,  or  with  large  samples,  on  a  clean  floor,  and  mixed 
well.  It  is  then  heaped  into  a  large  pile  and  divided  into  four 
quarters  by  means  of  a  thin  sheet  of  metal,  or,  if  the  sample  is 
small,  a  spatula  is  used.  Two  of  these  quarters  (these  diagonally 
opposite  each  other)  are  then  scraped  and  brushed  away  and  the 
two  remaining  ones  are  again  mixed,  divided  into  quarters  and 
two  of  these  rejected  as  before.  The  sample  will  now  represent 
one-quarter  its  original  bulk,  and  if  the  quartering  is  repeated 
again  one-eighth  its  bulk,  etc. 

Mechanical  appliances  for  quartering  have  also  been  devised. 
That  shown  in  Fig.  64  is  simple  and  easily  constructed  and  works 
nicely.  It  consists  of  a  cone  or  funnel,  A,  made  of  sheet  metal, 
terminating  in  a  short  piece  of  galvanized  iron  or  tin  pipe,  B. 
This  opens  into  a  wooden  box,  C.  The  top  of  the  box,  C,  is  loose 
so  that  the  funnel  and  top  may  be  removed  and  the  box  emptied 
when  necessary.  The  pipe,  B,  is  divided  into  four  sections  as 
shown  in  Fig.  64,  two  of  which,  f  and  g,  empty  into  the  box,  C, 
while  the  other  two,  h  and  i,  discharge  into  the  pans,  E±  and  E2, 
by  means  of  the  pipes,  Dl  and  D2.  In  using  this  sampler,  the  ma- 
terial to  be  quartered  is  poured  into  the  funnel  A,  and  dropping 
through  the  tube  B  is  divided  into  four  parts,  two  of  which  fall 
into  the  box  and  are  rejected,  while  the  other  two  go  into  the 
pans,  El  and  E2.  The  cone,  A,  should  be  kept  fairly  full  of  ma- 
terial and  stirred  all  the  time,  so  that  a  solid  stream  of  particles 
is  passing  through  the  pipe. 

Crushers. — Various  mechanical  contrivances  have  been  de- 
vised by  different  parties  to  lessen  the  labor  of  crushing  and  pul- 
verizing with  the  ordinary  hand  mortar.  One  of  these  is  to  fasten 
a  stout  spring  to  one  of  the  overhead  rafters  in  the  ceiling  of  the 


SMALL    CHEMICAL    LABORATORIES. 


sampling  room,  and  attach  the  pestle  to  the  other  end  of  this.  It 
is  claimed  by  those  who  use  this  device  that  the  spring  does  not 
perceptibly  add  to  the  force  required  to  strike  a  crushing  blow, 
while  it  does  greatly  aid  in  lifting  the  pestle.  Such  a  spring 
should  be  about  18  inches  long,  and  have  coils  i^  inch  in  diame- 
ter made  of  the  best  steel  spring  wire,  ^  inch  in  diameter.  This 


C 


Fig  64. — Automatic  Divider  for  Quartering  Samples. 

arrangement  is  of  course  only  intended  for  use  with  a  very  heavy 
pestle. 

Where  power  is  at  hand,  the  pestle  may  be  raised  by  means 
of  cams  and  allowed  to  fall  of  its  own  weight.  Such  an  arrange- 
ment does  not  seem  to  have  any  advantage  over  the  crushers, 
either  in  cost  or  effectiveness,  and  is  nothing  like  so  convenient. 
For  crushing  large  lumps  of  ore,  the  chilled  iron  plate  and  pestle 
shown  in  Fig.  65  will  be  found  useful.  Its  inside  dimensions  are 
24  x  24  x  3  inches,  and  the  walls  and  sides  are  3  inches  thick. 


SAMPLING  APPLIANCES.  91 

The  operator  stands,  in  using  this  plate,  and  merely  lifts  the  pestle 
and  allows  it  to  do  the  crushing  by  its  own  weight. 

Where  large  quantities  of  ore  have  to  be  broken  up,  small 
crushers  will  be  found  much  more  convenient  than  the  mortar 
and  pestle,  and  every  laboratory  which  handles  samples  as  large 
as  ten  pounds  and  over  should  be  provided  with  some  sort  of 
mechanical  crusher.  If  possible,  this  should  be  power  driven,  but 


I 


Fig.  05.— Chilled  Iron  Plate  and  Pestle  for  Crushing  Samples. 

even  if  it  has  to  be  operated  by  hand,  it  will  be  found  more  con- 
venient than  the  mortar  and  pestle. 

Figure  66  shows  the  Taylor  Hand  Crusher.  This  consists  of 
two  jaws,  one  of  which  is  stationary  and  one  of  which  is  operated 
by  the  hand  lever.  Both  jaws  are  faced  with  hard  white  iron. 
The  movable  jaw  has  horizontal  corrugations,  so  as  to  force  the 
material  to  be  crushed  down  at  each  stroke  of  the  lever.  This 
jaw  moves  in  both  a  vertical  and  horizontal  direction.  The  lever 


Fig.  GG. — Taylor's  Hand  Crusher. 

has  a  rubber  covered  hand  grip,  and  a  rubber  cushion  where  it 
strikes  the  bed-piece,  prevents  jar  and  noise.  The  jaws  are  3 
inches  wide  and  open  i^4  inches,  so  that  a  piece  of  material  3  x 
1^4  inches  can  be  crushed.  Forty  pounds  of  the  hardest  rock  can 
be  easily  crushed,  in  one  hour,  to  such  a  fineness  that  20  per  cent, 
of  it  will  pass  a  sieve  having  60  meshes  to  the  linear  inch  (No. 
6o-sieve).  The  jaws  can  be  so  adjusted  that  all  can  be  made  to 
pass  the  above  sieve.  The  crusher  can  be  easily  cleaned  and  kept 


92  SMALL    CHEMICAL    LABORATORIES. 

in  repair.  It  crushes  much  faster  than  a  mortar,  because  the  fine 
material  drops  out  into  the  pan  as  fast  as  produced,  and  does  not 
remain,  as  in  a  mortar,  to  deaden  the  blows  of  the  pestle.  This 
crusher  is  catalogued  at  $15.00  and  may  be  purchased  of  any 
dealer  in  chemical  supplies. 


Fig.  67.— Weather-head's  Crusher. 


Fig.  68.— Bosworth's  Crusher. 

Figure  67  shows  Weatherhead's  Crusher,  which  is  also  a 
pulverizer.  Its  operation  is  evident  from  the  cut. 

Figure  68  shows  a  Bosworth  Crusher,  which  may  be  operated 
either  by  hand  or  power.  The  Blake  Crusher  is  somewhat  similar 
to  the  Bosworth  Crusher. 

In  these  crushers  one  jaw  is  fixed  and  the  other  is  swung 


SAMPLING  APPLIANCES. 


93 


back  and  forth,  through  a  very  small  arc,  by  means  of  an  eccentric 
shaft,  revolved  by  either  the  hand  wheel  or  the  pulley.  The  shaft 
in  revolving  raises  and  lowers  a  rod  which  is  connected  by  tog- 
gles with  the  movable  jaw.  These  crushers  can  be  procured  in 
sizes  ranging  from  laboratory  size  up.  The  small  size  usually 
costs  about  $50.00. 

The  Bosworth  Crusher  has  been  much  improved  upon  of 
late,  particularly  with  respect  to  the  ease  with  which  it  can  be 
adjusted  and  cleaned.  Below  will  be  found  mention  of  three  of 
these  crushers. 


Fig.  69. — Case  Laboratory  Crusher. 

The  Case  Laboratory  Crusher  (patented  in  1903),  Fig.  69, 
was  especially  designed  to  meet  the  demand  for  a  low  priced, 
strong,  laboratory  crusher.  It  can  be  driven  by  either  hand  or 
power,  and  will  crush  from  100  to  200  Ibs.  of  ore  per  hour,  de- 
pending, of  course,  on  the  hardness  of  the  ore.  The  jaw  opening 
is  2l/2  by  3  inches  and  it  can  be  adjusted  quickly  from  a  fineness 
of  %  inch  to  20  mesh.  The  feed-  is  regular,  and  it  is  not  inclined 
to  cake  on  soft  material.  Messrs.  E.  H.  Sargent  &  Co.,  Chicago, 
handle  this  crusher  which  they  sell  at  $30.00,  hand  driven,  and 
$32.00,  fixed  for  power. 

Figure  70  shows  the  Calkins  Advance  Ore  Crusher,  manu- 


94 


SMALL    CHEMICAL    LABORATORIES. 


factured  "by  The  Calkins  Company,  Denver,  Colo.  One  of  the 
features  of  this  crusher  is  the  ease  with  which  it  can  be  cleaned. 
This  is  done  by  swinging  up  the  front  jaw  of  the  crusher  expos- 
ing the  sides  and  face  of  the  vibratory  jaw  and  giving  access  to 
all  parts  of  the  machine  to  which  material  being  crushed  may 
adhere.  The  adjustment  to  coarse  or  fine  crushing  is  made  at  the 
front  end  of  the  crusher.  This  machine  is  made  in  two  sizes ;  the 
smallest  has  a  jaw  opening  2.y2  x  3  inches,  weighs  170  pounds, 
and  is  listed  at  $30.0x3  net;  the  larger  size  has  a  jaw  opening  3  x 
4  inches,  weighs  280  pounds  and  is  listed  at  $60.00  net. 

The  "Lightning"  Crusher,  Fig.  71,  manufactured  by  F.  W. 
Baun  &  Co.,  Los  Angeles,  CaL,  is  also  a  very  efficient  crusher 


Fig.  70.— Calkins'  Advance  Ore  Crusher. 

which  may  be  adjusted  to  crush  fine  or  coarse.  This  crusher  is 
also  very  easily  cleaned,  as,  after  lifting  a  pin,  the  front  jaw 
may  be  swung  out  on  a  vertical  hinge  exposing  both  crushing 
plates  and  allowing  them  to  be  quickly  and  thoroughly  cleaned 
with  a  brush.  This  crusher  is  very  compactly  and  strongly 
built. 

Where  very  large  quantities  of  ore  have  to  be  crushed  a 
Gates  gyratory  crusher  will  be  found  most  useful.  These  are 
made  by  the  Allis-Chalmers  Co.,  Milwaukee,  Wis.,  in  a  variety 
of  sizes  and  types.  The  smallest  size  will  crush  500  Ibs.  of  ma- 
terial of  average  hardness  per  hour,  to  a  fineness  of  24  mch  or 
250  Ibs.  to  Y%  inch. 


SAMPLING  APPLIANCES. 


95 


Agate  Mortar. — For  finely  pulverizing  small  samples,  already 
reduced  by  means  of  the  iron  mortar  and  pestle  to  pass  a  No.  100 
sieve,  the  agate  mortar  is  indispensable;  except  when  the  ore  or 
mineral  is  very  soft,  when  a  Wedgwood  mortar  and  pestle  may 
be  used.  From  the  size  and  shape  of  the  ordinary  agate  mortar 
and  pestle  the  operation  of  grinding  is  very  tedious.  It  may  be 
greatly  facilitated,  however,  by  cutting  a  hole,  of  such  size  and 
shape  as  to  hold  the  mortar  firmly,  in  the  middle  of  a  block  of 
hard  wood,  a  foot  or  so  square.  The  pestle  is  then  fixed  in  a  piece 
of  round  brass  tubing  of  sufficient  bore  to  hold  it  firmly,  or  else 
in  a  round  hard  wood  handle. 


Fig.  71.— Braun's  Lightning  Crusher. 

Mechanically  Operated  Agate  Mortar. — Some  ten  or  fifteen 
years  ago  Mr.  Maunsel  White,  of  the  Bethlehem  Iron  Company, 
designed  a  mechanically  operated  agate  mortar  and  pestle  for  use 
in  the  laboratory  of  the  above  concern.  This  grinder  is  illustrated 
and  described  in  Blair's  "The  Chemical  Analysis  of  Iron." 

The  McKenna  Bros.  Brass  Co.,  Pittsburg,  Pa.,  have  also 
brought  out  a  mechanically  operated  agate  mortar  and  pestle.  This 
is  illustrated  in  Fig.  72.  It  consists  of  a  revolving  table  on  which 
the  agate  mortar  is  clamped,  while  the  agate  pestle  is  firmly  fixed 
in  a  shaft  revolving  at  a  slight  angle  from  the  vertical.  This  ma- 
chine reproduces  almost  exactly  the  motion  used  in  hand  grind- 
ing. The  spring  at  the  top  of  the  sliding  rod,  to  which  the  agate 


96         SMALL  CHEMICAL  LABORATORIES. 

pestle  is  fixed  at  the  bottom,  can  be  adjusted  to  give  any  desired 
pressure,  or  can  be  thrown  back  entirely  to  allow  the  pestle  to  be 
raised  in  removing  the  agate  mortar.  The  mortar  is  readily  re- 
moved by  loosening  a  set  screw  and  dropping  one  of  the  four  posts 
holding  the  mortar  in  place.  A  scraper  keeps  the  ore  in  the  center 

c- 


Fig.  72.— McKenna  Mechanically  Operated  Agate  Mortar  and  Pestle. 

of  the  mortar,  and  the  combined  rolling  and  sliding  motion  of  the 
pestle,  which  is  controlled  by  a  ball  and  socket  side  arm,  reduces 
the  hardest  ore  very  rapidly,  no  attention  being  required  from  the 
operator.  The  grinder  may  be  operated  by  any  convenient  power, 
of  which  not  to  exceed  J^  horse-power  is  required.  The  mortar 


SAMPLING  APPLIANCES. 


97 


used  has  a  diameter  of  about  4^4  inches.   These  mortars  were  in- 
troduced into  many  laboratories  and  gave  good  satisfaction. 

The  agate  mortar  is,  of  course,  intended  only  for  grinding 
very  small  quantities  (5  or  10  grams)  of  ore  at  a  time.  It  has 
one  great  advantage  over  other  forms  of  pulverizers  in  that  it  can 
be  used  to  reduce  the  hardest  ores  to  a  fine  powder  without  danger 
of  contamination  of  the  sample  from  the  wear  of  the  mortar  and 
pestle.  When  soft  materials,  such  as  coal  have  to  be  ground, 
large  Wedgwood  mortars  and  pestles  are  very  useful.  In  using 
these,  however,  the  material  should  be  merely  rubbed  between  the 


Fig.   73. — Braun's   Gyratory  Muller. 

pestle  and  the  mortar,  and  never  pounded,  for  fear  of  contamina- 
ting the  sample  with  splinters  of  porcelain. 

Gyratory  Muller. — Two  excellent  pulverizers,  one  of  which 
can  be  operated  by  hand,  are  manufactured  by  Messrs.  F.  W. 
Braun  &  Co.,  Los  Angeles,  Cal.  They  are  the  gyratory  muller 
and  the  disc  pulverizer.  The  first  of  these  is  driven  by  hand  and 
the  second  is  intended  to  be  power-driven  from  a  small  electric 
motor  or  the  mill  shafting. 

The  gyratory  muller  is  shown  in  Fig.  73.  In  this  muller  the 
grinding  is  done  by  a  ball  or  spherical  pestle  which  revolves  in  a 
semi-spherical  mortar  with  a  particular  twisting  motion.  This 
motion  is  imparted  to  the  rjestle  by  means  of  a  right  angle  clutch 


98          SMALL  CHEMICAL  LABORATORIES. 

extension.  The  material  is  rapidly  crushed  by  the  revolving  ball, 
and  the  twisting  motion  prevents  the  material  from  being  thrown 
ahead  of  the  ball,  by  centrifugal  force,  and  causes  it  to  discharge 
through  an  opening,  provided  for  that  purpose,  in  the  bottom  of 
the  mortar. 

A  coil  spring  around  the  ball  shaft  gives  tight  engagement 
between  the  surface  of  the  ball  and  the  mortar,  and  more  or  less 
compression  may  be  obtained  by  means  of  washers  above  the 
spring.  Loosening  he  thumbscrew  allows  the  bale  or  arch  to  be 
swung  back,  and  this  lifts  the  ball  from  the  mortar,  giving  access 
to  the  interior  for  cleaning.  This  machine  has  been  found  entirely 
satisfactory  where  large  or  small  quantities  of  material  are  to  be 
pulverized  to  a  given  size.  The  best  results  are  obtained  by 


Fig.    74.— Braun's   Disc    Pulverizer. 

screening  the  product  each  time,  for  if  this  is  not  done  the  finer 
particles  surround  the  larger,  preventing  them  from  being  pul- 
verized. This  appliance  differs  from  the  disc  pulverizer  de- 
scribed below,  as  it  is  necessary  to  feed  and  re-feed  several  times, 
according  to  the  material,  to  obtain  an  extremely  fine  powder. 
This  muller  is  priced  at  $35.00. 

Disc  Pulverizers. — Messrs.  F.  W.  Braun  &  Co.  have  recently 
brought  out  another  form  of  fine  grinder  or  pulverizer,  for  which 
they  claim  great  efficiency  and  which  they  call  a  Disc  Pulverizer, 
shown  in  Fig.  74.  In  this  machine  the  grinding  is  done  between 
a  stationary  and  a  revolving  disc.  The  stationary  disc  or  plate 
is  fastened  to  the  door  of  the  machine.  The  meshing  of  these 
discs  can  be  adjusted  so  as  to  regulate  the  fineness  to  which  the 
material  is  to  be  ground. 


SAMPLING  APPLIANCES.  99 

This  machine  will  pulverize  any  material  that  can  be  reduced 
to  pulp  on  the  old  style  bucking  board.  It  will,  with  one  feeding, 
pulverize  an  entire  ore  sample  to  any  desired  degree  of  fineness  up 
to  200  mesh  powder.  An  8-ounce  sample  of  ordinary  granite  rock 
can  be  reduced  to  100  mesh  in  one-half  minute.  Other  degrees 
of  fineness  may  be  obtained  in  proportionately  more  or  less  tirre. 
It  may  be  thoroughly  and  quickly  cleaned  after  each  sample  has 
been  fed.  The  adjustment  may  be  altered  for  the  desired  powder 
in  a  second.  It  is  dust  proof.  There  is  no  loss  of  material.  Its 
pulverizing  discs  wear  to  place.  The  wearable  parts,  which  have 
a  very  long  life,  are  renewable  and  easily  replaced.  The  discs  are 
made  of  hardened  steel  with  faces  ground  true.  The  bearings  of 


Fig.    75. — Calkins'    Advance    Disc    Sample    Grinder. 

the  revolving  disc  are  babbitted  and  extra  long.  Provision  is 
made  for  preventing  the  oil  from  entering  the  pulverizing  cham- 
ber. The  revolving  disc  is  tapered  from  its  face  to  the  shaft,  and 
is  also  machine  finished  to  prevent  fanning  of  material  when  in 
operation,  and  to  economize  power.  At  the  bottom  of  the  four 
sides  of  the  pulverizing  chamber,  lips  are  provided,  which  ensure 
the  discharge  of  material  into  the  pan  which  fits  closely  into  a, 
slide  beneath  the  discs.  This  machine  is  fed  through  the  spout  m 
the  door,  and  will  take  ore  *4  mesh  and  smaller,  and  reduce  it  all 
at  one  feeding  to  any  desired  mesh.  Price  of  the  machine,  com- 
plete, $85.00. 

The  Calkins  Advance  Disc  Sample  Grinder  is  shown  in  Fig. 
75-    It  consists  of  a  main  frame  or  support  to  which  is  secured  a 


100  SMALL    CHEMICAL    LABORATORIES. 

stationary  disc.  A  rocker-arm,  carrying  a  driven  shaft,  to  one 
end  of  which  is  secured  a  grinding  disc,  and  having  driving  gears 
and  fly  wheel  at  the  opposite  end,  is  pivotally  journaled  to  the 
main  frame  of  the  machine.  When  in  operation  the  disc  on  the 
driven  shaft  is  given  a  double  motion,  rotating  and  vibrating.  The 
oscillating  or  vibrating  motion  is  created  by  means  of  an  eccentric 
on  the  driven  shaft  which  by  rotating  against  a  roller  which  is 
journalled  to  the  main  frame  of  the  machine,  causes  the  rocker 
arm  carrying  the  driven  disc  shaft  to  rise  and  fall. 

The  cam  or  eccentric  is  not  keyed  to  the  disc  shaft  but  is 
slowly  rotated  around  the  disc  shaft  by  means  of  gears  so  as  not 


Fig.  76.— Abbe  Jar  Mill. 

to  limit  the  oscillating  motion  of  the  rocker  arm  and  disc  to  a 
contracted  orbit  of  travel.  This  double  motion  is  very  destructive 
to  the  ore  particles  which  are  fed  between  the  discs  from  a  hopper 
leading  to  an  opening  through  the  stationary  disc,  and  not  only 
alters  the  position  of  the  rolling  particles  between  the  discs,  but 
prevents  the  discs  from  becoming  concentrically  grooved,  which 
would  occur  should  the  disc  or  discs  have  a  rotary  motion  only. 

The  rocker  arm  carrying  the  driven  shaft  and  disc  may  ue 
lifted  or  swung  over,  clear  of  the  opposing  disc,  to  allow  both 
discs  to  be  cleaned  of  any  adhering  particles  of  any  sample  pre- 
viously crushed,  which  might  otherwise  "salt"  the  ^ucceeding 
sample. 

Adjustment  for  coarse  or. fine  grinding  is  made  by  means  of 
lock  nuts  on  the  pivot  shaft,  which  secures  the  rocker  arm  to  tH$ 


SAMPLING  APPLIANCES.  IOI 

frame  of  the  machine.  The  lock  nuts  bear  against  the  part  of  the 
frame  through  which  the  end  of  the  pivot  shaft  passes,  and  re- 
tain the  rocker  arm  and  rotary  disc  in  any  desired  degree  of  ad- 
justment relative  to  the  stationary  disc.  The  price  of  the  pul- 
verizer is  $50.00  and  the  weight  175  pounds. 

Jar  Mill. — The  Abbe  Engineering  Co.,  220  Broadway,  New 
York,  manufacture  a  small  jar  mill  which  is  shown  in  Fig.  76. 
This  mill  consists  of  a  porcelain  jar,  13  x  i2l/2  inches,  held  se- 
curely in  a  cast  iron  frame  by  brass  bands.  Two  of  these  bands 
are  fastened  at  each  end,  but  the  third  is  held  in  place  by  a  thumb- 
nut,  which  allows  the  jar  to  be  taken  from  the  frame.  The  frame 
is  provided  with  a  shaft  at  either  end,  and  is  revolved  by  a  pulley 
as  shown.  The  jar  is  closed  by  a  porcelain  cover,  which  is  clamp- 
ed tightly  on  the  top  of  the  former,  a  tight  joint  being  secured  by 
means  of  a  rubber  washer.  The  jar  is  half  rilled  with  porcelain 
balls.  As  the  jar  is  concentric  with  the  axle  of  the  frame,  the 
grinding  is  done  by  the  pounding  of  the  pebbles  as  the  jar  re- 
volves. The  speed  of  the  latter  is  from  40  to  50  revolutions  per 
minute,  about  23  Ibs.  of  porcelain  balls  are  used  for  a  charge  and 
about  15  Ibs.  of  matt.idl  can  be  ground  at  a  time.  The  mill  is 
intended  to  be  power  driven,  and  may  be  run  by  a  small  motor. 

These  mills  may  be  used  for  a  great  variety  of  laboratory 
work,  and  are  very  useful  where  large  samples  have  to  be  very 
finely  pulverized,  as  it  is  possible  to  grind  extremely  fine  with 
them.  Owing  to  the  difficulty  of  cleaning  the  pebbles  they  are 
more  used  for  experimental  work  than  for  preparing  analytical 
samples.  The  pebbles  may  be  separated  from  the  ground  ma- 
terial by  using  a  large  coarse  mesh  sieve,  and  they  may  be  cleaned 
either  by  brushing  with  a  stiff  brush,,  or  by  washing  with  water 
or  acid,  or  by  grinding  and  discarding  a  little  of  the  material  to 
be  pulverized. 

This  size  jar  mill  is  priced  at  $60.00  and  weighs  175  Ibs.  The 
Abbe  Engineering  Co.  make  a  number  of  mills  of  this  type,  rang- 
'ng  in  capacity  from  the  size  mentioned  up  to  one  of  several  tons 
.Opacity  per  hour. 


CHAPTER    XIII. 
ASSAY    FURNACES    AND    ACCESSORIES. 

Assay  furnaces  are  made  to  use  three  kinds  of  fuel — gaseous, 
liquid  and  solid.  Those  using  gas  are  very  little  employed,  usually 
only  in  city  laboratories  where  but  a  few  assays  are  made.  They 
are,  of  course,  very  convenient  when  occasional  assays  are  made, 


Fig.  77.— Assay  Furances  and  Table — Buffalo  Dental  Mfg.  Co. 


ASSAY  FURNACES  AND  ACCESSORIES. 


I03 


Fig.  78.— Roasting  Furnace— Buffalo  Dental  Mfg.  Co. 


OSL 


Fig.  79. — Crucible  Furnace — Buffalo  Dental  Mfg.   Co. 

as  in  the  laboratory  of  a  consulting  chemist,  who  is  sometimes 
called  upon  to  determine  the  value  of  a  gold  or  silver  ore. 

Perhaps  the  best  of  these  gas  heated  furnaces  are  those  manu- 
factured by  the  Buffalo  Dental  Manufacturing  Co.,  Buffalo,  N.  Y. 
For  assaying,  three  of  these  furnaces  will  be  needed  (see  Fig.  77). 


104  SMALL    CHEMICAL    LABORATORIES. 

One  for  roasting  sulphide  ores,  one  for  crucible  fusions  and  one 
for  cupellation.  Figure  78  shows  the  roasting  furnace,  which  is 
known  as  "No.  63,  Direct  Draft  Crucible  Furnace."  It  consists 
of  a  fire  clay  body  strapped  with  sheet-iron  bands,  and  provided 
with  a  Fletcher  burner.  The  opening  at  the  top,  which  is  pro- 
tected when  not  in  use  by  a  cover,  is  to  allow  the  heat  to  have  full 
play  upon  the  roasting  dish  placed  upon  it.  The  hot  flame  passes 
through  the  furnace  and  up  the  chimney.  When  set  up  this"  fur- 
nace should  have  a  hood  or  funnel  placed  over  it  as  shown  in 
Fig.  77.  This  carries  off  the  odors  and  gases  given  off  by  the 
ores.  The  pipe  and  hood  should  be  provided  with  dampers.  This 
furnace  is  listed  at  $12.00. 


Fig.    SO. — Cupellation   Furnace — Buffalo    Dental    Mfg.    Co. 

The  crucible  furnace  is  shown  in  Fig.  79.  The  furnace  is 
heated  by  a  No.  15  Fletcher  burner  and  is  made  in  five  parts — an 
outer  cylinder  of  fine  clay,  which  is  covered  by  a  removable  fire 
clay  top  with  handle  attached,  and  rests  upon  a  bed  plate,  also 
made  of  fire  clay,  which  has  a  hole  in  it  through  which  the  flame 
passes,  a  graphite  inner  cylinder  and  a  combustion  chamber  below. 
This  furnace  is  listed  as  "No.  15  Crucible  Furnace"  and  priced 
at  $16.00. 

The  cupellation  and  scorification  furnace  is  shown  in  Fig.  80. 
This  furnace  was  designed  by  Mr.  Walter  Lee  Browne,  and  is 
described  by  him  in  his  "Manual  of  Assaying."  In  form  it  is  al- 
most that  of  the  reverberatory  furnace,  the  movable  bricks  when 


ASSAY  FURNACES  AND  ACCESSORIES. 


105 


in  place  being  the  roof.  In  the  interior,  upon  the  bottom,  are  four 
little  wedge-shaped  bridges  of  fire  clay,  which  are  movable,  and 
upon  them  rests  a  false  bottom  or  floor,  also  movable.  The  latter 
corresponds  to  the  muffle  bottom  of  an  ordinary  furnace  and  upon 
it  is  done  all  the  work.  The  furnace  is  heated  by  a  No.  16  burner, 
and  is  made  by  the  Buffalo  Dental  Manufacturing  Co.  It  is  called 
by  them  "No.  630  Monitor  Furnace"  and  is  listed  at  $18.00. 


The 


Fig.   81.— Muffle   Furnace — Buffalo   Dental   Mfg.    Co. 

The  table  is  of  pine  and  is  covered  with  fire  clay  tile, 
whole  outfit,  table  and  furnace,  is  listed  at  $75.00. 

Another  small  gas-fired  assay  furnace,  also  manufactured  by 
the  Buffalo  Dental  Manufacturing  Co.,  is  shown  in  Fig.  81.  It 
is  made  in  four  sizes,  the  smallest  priced  at  $17.00,  and  having 
an  inside  muffle  space  3x4x2^,  and  the  largest  costing  $45.00 
and  having  a  muffle  space  of  6  x  Sy2  x  4%.  A  simple  outfit  for  as- 
saying would  consist  of  the  No.  4  size  of  this,  having  a  muffle 
space  3%  x  SH  an(l  priced  at  $20.00,  for  the  cupelling  and  the 


io6 


SMALL    CHEMICAL    LABORATORIES. 


crucible  furnace  referred  to  before,  which  could  be  made  to  do 
the  roasting  also  if  set  up  with  a  hood  over  it.  Some  assayers, 
however,  do  not  roast  their  ores. 

Liquid  Fuel  Furnaces. — A  large  number  of  very  convenient 
assay  furnaces  designed  for  the  use  of  gasolene  are  now  on  the 
market,  and  where  much  assaying  is  done,  and  the  assayer  is  not 
permanently  located  and  gasolene  can  be  obtained,  nothing  quite 
takes  their  place.  They  are  small  and  can  be  quickly  heated. 
They  can  also  be  easily  transported  from  place  to  place.  They 


Fig.  82.— L.  &  C.  Combination  Furnace— F.  W.  Braun  &  Co. 

are  designed  for  either  crucible  fusions  or  for  cupellations  or  for 
both.  The  latter,  so  called  "combination  furnaces,"  are  the  most 
convenient  and  economical.  In  them  the  fusion  is  carried  on  in 
one  part  of  the  furnace  while  the  cupellation  is  being  done  in  the 
muffle. 

Fig.  82  shows  the  L.  &  C.  combination  furnace,  manufac- 
tured by  the  F.  W.  Braun  Co.,  Los  Angeles,  Cal.  This  furnace 
consists  of  a  compartment  for  crucibles  at  one  end  and  the  muffle 
at  the  other.  It  has  a  burner  hole  at  either  end  and  is  mounted 
on  a  swivel  which  allows  the  furnace  to  be  revolved  so  that  the 


ASSAY  FURNACES  AND  ACCESSORIES.  107 

burner  may  be  inserted  in  either  one.  Usually  the  burner  is  first 
inserted  in  the  crucible  end  long  enough  to  make  one  melt;  the 
furnace  is  then  revolved  and  the  burner  inserted  in  the  muffle 
end.  From  this  time  on  the  melting  and  cupellation  may  be  car- 
ried on  at  the  same  time  without  revolving  the  furnace.  A  divid- 
ing brick  is  furnished,  to  be  placed  between  the  melting  and  muffle 
departments,  if  only  one  is  to  be  heated.  A  small  trap-door  is 
placed  in  the  bottom  of  the  crucible  compartment,  and  if  a  spill 
occurs  this  may  be  opened,  the  bottom  punched  out  and  a  new  one 
of  fire  clay  and  sawdust  put  in.  Oxidation  in  the  muffle  is  secured 
by  means  of  a  fire  brick  flue  connecting  the  muffle,  through  a  hole 
in  the  latter,  with  the  main  flue  by  means  of  a  pipe  at  the  back 


Fig.  83. — Gary  Combination  Furnace  and  Burner — F.  W.  Braun  &  Co. 

of  the  furnace,  as  shown.     The  pipe  is  provided  with  a  damper 
to  regulate  the  draft  when  the  buttons  in  the  cupel  are  opening. 

These  furnaces  are  intended  to  be  heated  by  the  "Sunset" 
burner,  made  by  the  same  firm.  The  arrangement  of  furnace  and 
burner  is  illustrated  in  Fig.  83.  The  furnace  itself  should  be 
raised  slightly  from  the  table,  as  shown,  and  the  latter  should  be 
covered  with  asbestos,  or  better  still,  with  fire  tiles.  The  con- 
crete table  top  mentioned  in  Chapter  II.  is  suited  to  this,  particu- 
larly if  coarse  calcined  magnesia  or  asbestos  fibre  is  used  in  place 
of  sand,  in  the  proportions  of  about  three  parts  to  one  of  cement. 
This  furnace  is  made  in  a  number  of  sizes  ranging  from  a 
x  8  x  3-inch  muffle,  holding  two  No.  G  crucibles  to  one  having 


io8 


SMALL    CHEMICAL    LABORATORIES. 


a  muffle  6x9x4  inch  and  taking  four  No.  G  crucibles.  The 
price  of  the  latter  size  together  with  burner,  gasolene  tank,  pump, 
etc.,  is  $44.50.  A  furnace  made  similar  to  the  one  described  above 
called  the  "Gary  Combination  Furnace,"  is  to  be  heated  by  the 
"Gary"  burner,  a  more  efficient  burner  than  the  "Sunset."  The 
price  of  the  complete  Gary  outfit  as  shown  in  Fig.  83  is  $55.00, 
exclusive  of  the  table. 

The   "Advance   Combination   Melting  and   Muffle   Furnace 
No.   10,"  manufactured  by  The  Calkins  Company,  is  shown  in 


Fig>  84.— Advance  Combination  Furnace— The  Calkins  Co. 

Figs.  84  and  85.  This  furnace  consists  of  a  circular  crucible 
chamber  above  which  is  the  muffle,  Fig.  84.  Access  to  the  crucible 
chamber  is  had  from  either  side  of  the  furnace  through  covered 
apertures.  The  flame  is  shot  into  the  crucible  chamber  at  a  tan- 
gent to  the  inner  wall  of  the  furnace,  Fig.  85,  and  swirls  around 
the  crucibles.  It  is  claimed  that  by  not  impinging  the  flame  on 
the  crucibles  the  life  of  the  latter  is  thereby  greatly  increased  and 
that  the  products  of  combustion  rising  unobstructed  around  the 
muffle,  the  latter  is  uniformly  heated.  The  muffle  is  ventilated, 


ASSAY  FURNACES  AND  ACCESSORIES. 


109 


as  shown  in  Fig.  84.  The  furnace  itself  is  encased  in  an  iron 
jacket  and  is  provided  with  a  removable  bottom  to  allow  replace- 
ment of  the  floor  of  the  crucible  chamber.  The  furnace  is  16 
inches  in  diameter  and  21  inches  high  and  weighs  180  pounds. 
The  muffle  is  4  x  6  x  12  inches  and  the  crucible  chamber  is  12 


Fig.  85.— Advance  Combination  Furnace — The  Calkins  Co. 

inches  inside  diameter  and  8  inches  high.  Starting  with  a  cold 
furnace,  a  good  working  heat  can  be  obtained  in  20  minutes  and 
the  muffle  will  be  ready  for  cupelling  before  the  melt  is  completed. 
The  furnace  is  heated  by  an  "Advance"  hydrocarbon  burner.  The 
price  of  the  furnace  above  is  $25.00  or  of  furnace,  burner,  7^- 
gallon  gasolene  tank  and  pump,  is  $48.00.  The  "Advance"  fur- 


Fig.  86.  Fig.  87. 

Crucible   Furnaces— The   Hoskins   Co. 

nace  is  made  in  two  smaller  sizes,  one  of  which  costs  $20.00  and 
the  other  $16.00. 

The  Hoskins  Company,  93  Erie  St.,  Chicago,  111.,  make  sev- 
eral forms  of  gasolene-heated  assay  furnaces.  Figures  86-  and  87 
illustrate  crucible  furnaces  of  which  the  first  is  intended  for  only 
one  crucible,  the  second  is  made  in  two  sizes  taking  respectively 


no 


SMALL    CHEMICAL    LABORATORIES. 


two  and  four  crucibles.  Fig.  88  shows  the  muffle  furnace.  The 
price  of  the  crucible  furnace  for  one  crucible,  muffle  furnace,  and 
one  gallon  blow  pipe  outfit,  complete,  is  $40.00.  Their  combina- 
tion furnaces  are  shown  in  Fig.  89  and  Fig.  90.  The  first  fur- 
nace shown  is  very  light  and  portable  and  is  intended  for  pros- 
pectors. It  is  also  of  use  when  only  an  occasional  assay  is  made. 
On  the  right  of  Fig.  89  the  furnace  is  shown  prepared  for  crucible 


Fig.    88.— Muffle    Furnace- 
The    Hoskins    Co. 


Fig.   89. — Prospectors'    Combination 
Furnace — The   Hoskins   Co. 


work.  By  lifting  off  the  cover  and  substituting  the  part  with  the 
muffle  opening,  and  sliding  into  this  the  muffle,  the  furnace  is  pre- 
pared for  cupelling  or  scorification.  The  muffle  is  6  x  3^2  x  2^2 
and  the  crucible  furnace  is  4  inches  in  diameter  and  5^2  inches 
deep.  Its  price  with  ^-gallon  blow  pipe  outfit  is  $30.00.  The 
combination  furnace,  shown  in  Fig.  90,  is  made  in  two  sizes,  the 


Fig.  90.— Combination  Furnace— The  Hoskins  Co. 

smaller  of  which  has  a  muffle  6  x  3^  x  2j/£  inches  and  a  crucible 
compartment  large  enough  for  one  fusion.  The  larger  size  is  in- 
tended for  four  No.  F  crucibles  and  has  a  muffle  10  x  6  x  4  inches. 
The  price  of  the  smaller  furnace  is,  with  ^-gallon  blow  pipe  out- 
fit, $33.00,  and  of  the  larger  one  with  a  gallon  blow  pipe  outfit,  is 
$46.00. 


ASSAY  FURNACES  AND  ACCESSORIES  JTT 


Fig.    91. — Battersea    Assay    Furnace. 


Fig.   92.— Brown's   Portable   Assay   Furnace. 


112  SMALL    CHEMICAL    LABORATORIES. 

Portable  Coal-Fired  Furnaces. — Of  the  portable  coal-fired  fur- 
naces, Bosworth's,  the  Battersea  and  Brown's  forms  are  all 
extensively  used  in  this  country.  The  Battersea  and  Bosworth's 
furnaces  are  very  similar  and  are  made  of  fire  clay,  in  sections, 
bound  together  with  iron  bands.  They  are  mufflle  furnaces  ex- 
clusively, but  they  are  made  in  large  sizes  and  in  these  latter 
crucible  melts  can  be  made  in  the  muffle.  These  two  furnaces  cost 
about  the  same,  the  price  ranging  between  $30.00  and  $40.00  for 
the  various  sizes.  The  Battersea  is  shown  in  Fig.  91.  Brown's 
Portable  Assay  Furnace  is  illustrated  in  Fig.  92.  It  consists  of  a 
nearly  square  sheet  iron  frame,  28  inches  high,  16  inches  wide, 
and  14  inches  deep,  lined  with  fire  brick.  The  cover  is  cast  iron, 
as  are  also  the  doors  to  the  muffle  and  ash  pit.  In  the  muffle  door 
is  a  window  filled  with  mica  so  that  the  operations  going  on  in- 
side the  muffle  may  be  observed  when  the  door  is  closed.  The 
ash  pit  doors  are  provided  with  wheel  openings  to  further  regulate 
the  draft.  The  grate  is  formed  of  cast-iron  bars  resting  upon  a 
cast-iron  frame.  It  is  made  for  a  muffle  12  inches  long,  6  inches 
wide  and  4  inches  high,  and  weighs  155  Ibs.  It  costs  $20.00 
boxed  for  transportation.  This  furnace  is  also  made  in  a  larger 
size,  taking  a  muffle  15  x  9  x  6  inches,  weighing  300  pounds  and 
costing  $35.00. 

A  small  furnace  called  the  uJac^ass"  ^s  made  by  the  Denver 
Fire  Clay  Co.  This  furnace  is  somewhat  similar  to  Brown's 
furnace.  It  is  much  lighter,  however,  weighing  100  Ibs.  It 
takes  the  same  size  muffle  and  costs  about  the  same. 

Permanent  Coal-Fired  Furnaces. — In  the  laboratories  of  mines 
and  smelters,  where  many  assays  are  a  part  of  every  day's  work, 
the  proper  furnaces  are  those  built  of  brick.  One  of  the  best  of 
these  is  that  described  by  H.  W.  Parmelee1  and  used  in  the  assay 
office  of  Mr.  J.  I.  Brown,  Cripple  Creek,  Colo.,  by  whom  it  was 
designed.  The  construction  of  the  furnace  is  evident  from  Fig. 
93,  and  its  good  points  are  thus  summed  up  by  Mr.  Parmelee: 

First,  it  has  larger  capacity  than  the  ordinary  furnace,  being 
capable  of  being  built  for  either  four  or  five  muffles.  This  en- 
ables the  operator  to  conduct  several  different  operations  in  the 
furnace  at  the  same  time,  thus  greatly  hastening  the  completion 
of  the  day's  work.  Fusion,  scorification  and  cupellation  can  be 
carried  on  at  the  same  time,  and  by  constantly  advancing  the 

Western  Chemist  and  Metallurgist,  III.   (1906),  179. 


ASSAY  FURNACES  AND  ACCESSORIES.  113 

assay  through  the  necessary  stages,  it  is  possible  to  run  through 
a  large  number  of  samples.  Fusions  are  made  in  the  lower  and 
upper  muffles  directly  over  the  fire  box ;  scorifications  in  the  next 
right-hand  muffle  and  cupellations  in  the  last.  The  theoretical 
capacity  of  this  four-muffle  furnace  is  90  assays  per  hour.  Practi- 
cally, Mr.  Brown  has  repeatedly  handled  400  assays  per  day  of 
10  hours,  and  states  that  the  furnace  could  easily  be  made  to  turn 
out  between  500  and  600  assays  per  day  of  10  hours. 


SECTION  B  B  SECTION  A  A 

Fig.  93. — Four  or  Five  Muffle  Assay  Furnace — Mr.  J.  I.   Brown. 

Second,  it  has  a  sufficiently  large  combustion  chamber  to  per- 
mit of  almost  complete  combustion  of  the  gases  before  they  escape 
into  the  flue.  This  means  that  the  full  effect  of  the  heat  is  re- 
ceived, with  the  result  stated  in  the  preceding  paragraph.  Five 
tons  of  coal  per  month  are  required  to  operate  this  furnace  to  its 
full  capacity,  running  ten  hours  per  day. 

Third,  it  is  provided  with  a  sample  dryer,  which  is  a  valua- 
ble adjunct  when  large  numbers  of  mine  samples  are  to  be  assayed. 


II4  SMALL    CHEMICAL    LABORATORIES. 

This  sample  dryer  makes  use  of  the  heat  above  the  muffles,  and 
has  greater  capacity  than  a  hot  plate  or  similar  contrivance,  at 
the  same  time  being  absolutely  inexpensive. 

Fourth,  the  fire-clay  linings  are  conveniently  replaced  when 
burned  out.  The  front  of  the  furnace  surrounding  the  muffles  is 
made  of  the  ordinary  moulded  blocks  found  on  the  market  espe- 
cially for  this  purpose.  These  can  be  removed  and  the  inside  of  the 
furnace  is  then  open  for  the  purpose  of  replacing  the  burned-out 
interior  layer  of  fire  brick.  It  will  be  noticed  in  this  connection 
that  between  the  pressed-brick  body  of  the  furnace  and  the  fire- 
brick interior  there  is  a  i-inch  air  space.  This  permits  of  the  suc- 
cessive expansion  and  contraction  of  the  fire  brick  without  plac- 
ing the  stress  on  the  outside  walls  and  tie-rods. 

Fifth,  it  is  a  forced-draft  furnace,  the  blast  being  supplied 
by  an  electrically-operated  blower.  To  prevent  the  burning  out 
of  the  grate  bars,  which  would  ensue  under  the  great  heat  gen- 
erated, the  ash-pit  is  provided  with  a  cement  water  pit  which  is 
kept  full  with  water  up  to  the  level  of  the  ash-pit  door. 

The  materials  used  in  the  construction  of  the  furnace  are 
those  commonly  used  everywhere.  The  outside  walls  are  of  red- 
pressed  brick.  The  inner  linings  are  of  fire  brick,  and  the  lining 
of  the  ash  pit  is  of  cement." 

Fig.  94  shows  a  superimposed  double-muffle  assay  furnace1 
used  by  some  of  the  lead-silver  mining  companies  of  Washington 
and  Idaho.  Two  furnaces  are  built,  one  on  either  side  of  the 
stack,  only  one  being  used  at  a  time,  each  being  large  enough  to 
do  the  entire  work  of  a  large  mine.  The  furnace,  when  once 
started,  is  used  from  day  to  day  until  burned  out,  lasting  from  19 
to  22  months.  The  second  furnace  is  then  started  while  the  first 
is  being  repaired.  By  building  double,  one  furnace  can  always  be 
ready.  The  repairing  of  a  furnace  requires  the  labor  of  a  mason 
and  helper  from  two  to  two  and  a  half  days.  The  stack  will  not 
require  repairing. 

The  fuel  used  is  soft  coal.  The  consumption  ranges  from  175 
to  250  Ibs.  per  day,  and  the  assays  made  will  range  from  75  to  150 
of  lead  and  silver.  This  furnace  can  be  brought  to  a  proper  heat 
for  work  in  45  min.,  but  two  hours  are  usually  taken.  The  draw- 
ing plainly  shows  all  dimensions. 

The  grate-bars  are  of  cast  iron,  as  well  as  all  doors,  which 

Ulysses  B.   Hough,   in  Engineering  and  Mining  Journal,   June  15,    1905. 


ASSAY  FURNACES  AND  ACCESSORIES. 


Fig.  94.— Double  Muffle  Furnace — Mr.  Ulysses  B.  Hough' 


Ii6  SMALL    CHEMICAL    LABORATORIES. 

are  lined  with  cast  plates  perforated  by  ^-inch  holes.  The  lining 
only  is  replaced  from  time  to  time.  The  outside-  should  be  se- 
curely stayed,  as  shown.  The  rods  are  to  be  made  with  a  nut  in 
one  end  and  an  eye  in  the  other.  In  this  furnace  both  muffles  heat 
alike,  work  being  done  in  one  as  well  as  in  the  other. 

Crucibles,  Scorifiers  and  Cupels. — Crucibles  for  the  assay  of 
gold,  silver  and  lead  ores  are  made  of  fire  clay.  They  are  made  in 
two  forms,  round  and  triangular.  For  an  ordinary  crucible  charge 
of  one  assay  ton  of  ore  and  fluxes  a  crucible  5  inches  high  and  3 
inches  in  diameter  can  be  used.  The  Battersea  crucibles  go  by 
letters  as  follows: 

Size C      D       E      F         G       H       J 

Height 3/^4        4^     5         5H     S7A     6^  inches 

Diameter 2%     2%     2%     3         3^     3%     4^8  inches 

The  crucibles  made  by  the  Denver  Fire  Clay  Co.  are  known  as 
"5  gram,"  "10  gram,"  etc.,  crucibles,  as  follows: 

Capacity 5         10         15         20         30         40  grams 

Height 25/8       3  3/^       33A       43A       55/8  inches 

Diameter 2^       2^3       2%       3  3%       3^3  inches 

A  low  form  3O-gram  crucible  3%  inches  high  and  3^  inches 
in  diameter,  is  also  obtainable  for  fusions  made  in  a  small  muffle. 

Scorifiers  are  made  of  fire  clay  and  run  in  sizes  from  T/2  inch 
to  4  inches  in  diameter.  Those  2^4  or  3  inches  are  most  used  and 
are  suited  to  changes  from  1/5  to  y*  assay  ton.  For  scorification 
and  to  reduce  a  too  large  lead  button  the  2% -inch  size  is  well 
suited. 

Cupels  are  made  of  bone  ash  and  may  be  made  by  the  assayer 
himself  or  they  may  be  purchased.  A  cupel  should  be  about  11/3 
times  the  weight  of  the  lead  button  to  be  cupelled.  A  cupel  il/2 
inches  in  diameter  is  a  good  size. 

Miscellaneous  Assay  Laboratory  Equipment. — The  rest  of  the 
equipment  of  the  assay  laboratory  has  much  of  it  been  described 
elsewhere.  If  the  cupels  are  made  by  the  assayer,  a  machine  for 
this  purpose  will  be  needed.  Figs.  95,  96  and  97  show  the  one 
made  by  F.  W.  Braun  &  Co.,  Los  Angeles,  California. 

This  machine  consists  of  a  hopper  to  hold  the  moistened  bone 
ash,  and  _a  removable  disc  with  a  number  of  holes  which  are  auto- 
matically filled  and  brought  into  position  under  the  plunger.  To 
operate,  the  bone  ash  is  properly  moistened  and  placed  in  the 


ASSAY  FURNACES  AND  ACCESSORIES.  117 

hopper.  In  this  latter  is  a  small  wheel  with  a  rubber  rim  that 
keeps  the  material  stirred  up  and  fills  the  moulds.  The  lever  handle 
is  then  raised  and  the  filled  mould  brought  beneath  the  plunger  by 
means  of  the  handle  on  the  lower  disc.  See  Fig.  95.  The  down- 
ward motion  of  the  lever  handle  compresses  the  cupel  (see  Fig. 
96)  and  by  pulling  the  disc  handle  in  a  reverse  direction  to  that 
formerly  given  it,  the  opening  in  the  lower  disc  is  brought  beneath 
the  cupel,  and  further  pressure  on  the  lever  handle  brings  a  new 
system  of  levers  into  action,  expelling  the  cupel ;  which  may  be 
caught  in  the  hand  (see  Fig.  97).  An  automatic  attachment  stops 
the  discs  at  the  proper  points,  and  an  adjusting  device  is  arranged 
for  giving  different  degrees  of  compression. 


Fig.    ',).">.— Braun's    Cupel    Machine— Filling    the    Mould, 

Cupels  of  five  various  sizes  and  depths  may  be  made  by  using 
interchangeable  discs  and  dies,  which  are  easily  adjusted  to  the 
machine. 

Its  list  price  is  $37.50  fitted  for  making  one  size  cupels.  Dies 
and  discs  for  other  sizes  are  $10.00  per  size. 

The  bone-ash,  which  can  be  purchased  in  bulk,  is  moistened 
with  sufficient  of  a  strong  solution  of  carbonate  of  potash  in  warm 
water  to  make  it  of  about  the  consistency  of  damp  sand.  It  should 
not  be  pasty,  but  should  show  the  finger  prints,  and  adhere  well 
together  when  squeezed  in  the  hand.  The  cupels  should  be  dried 
slowly  to  avoid  cracking. 

For  removing  the  cupels,  scorifiers  and  crucibles  from  the 
furnace,  tongs  will  be  needed.  These  are  made  in  a  variety  of 


iiS 


SMALL    CHEMICAL    LABORATORIES. 


forms  which  are  illustrated  in  catalogues  of  assay  supplies.  For 
lifting  crucibles,  when  the  operator  is  above  them  a  pair  of 
"basket"  tongs  are  best  suited,  while  for  removing  them  from  a 
muffle  a  pair  of  double  bent  tongs  are  best.  Cupped  lip,  or  lap 
lipped  cupel  tongs  grip  the  cupel  most  firmly;  the  former  will 
allow  the  moving  of  the  cupel  from  the  back  to  the  front  of  the 
furnace,  and  when  the  muffle  is  full  of  cupels.  Both  the  cup  and 
lap-lipped  tongs  grip  the  cupel  much  tighter  than  the  plain  lipped. 
Judson  has  devised  tongs  for  use  with  both  cupels  and  scorifiers 


H»t!:'.!ll;,.iii|:  .  IT.;,;!'!  ' 


Fig.  96. — Braun's  Cupel  Machine — 
Compressing  the  Cupel. 


Fig.   97. — Braun's  Cupel   Machine 
—Expelling  the  Cupel. 


which  are  convenient.  They  are  described  in  Brown's  Manual  of 
Assaying  and  listed  by  Eimer  &  Amend. 

Scorification  moulds  are  also  used  into  which  the  contents  of 
scorifiers  are  poured  in  order  that  they  may  cool  quickly.  They 
are  made  of  iron  and  are  illustrated  in  all  catalogues  of  assay 
appliances. 

A  muffle  scraper  is  useful  for  scraping  out  the  muffle  after 
a  spill.  This  consists  of  a  piece  of  i/i6-inch  sheet  iron,  6x6 
inches,  bent  at  right  angles,  one  inch  from  the  end  and  riveted  to 
an  iron  rod  y^  inch  in  diameter  and  3  ft.  long. 


CHAPTER  XIV. 
MISCELLANEOUS    LABORATORY   EQUIPMENT. 

Aspirators. — The  simplest  form  of  aspirator  consists  of  two 
large  bottles,  a,  Fig.  98,  both  of  which  are  tightly  stoppered  with 
rubber  stoppers.  Through  each  of  these  stoppers  pass  two  tubes, 
one  reaching  from  a  few  inches  outside  to  within  a  fraction  of 
an  inch  of  the  bottom  of  the  bottle,  the  other  reaching  to  just  in- 
side the  stopper.  The  two  long  tubes  are  joined  by  rubber  tubing 
and  the  flow  of  water  through  this  is  regulated  by  a  Hoffman 
clamp  on  the  tube.  If  air  is  to  be  sucked,  the  short  tube  of  the 
upper  bottle  is  to  be  connected  with  the  apparatus  from  which 
the  air  is  to  be  drawn.  If  air  is  to  be  forced  through  something, 
connectic  ide  between  the  latter  and  the  short  tube  of  the 

lower  bottle. 

An  improvement  on  the  above  is  a  pair  of  regular  aspirator 
bottles.  These  consist  of  bottles  having  a  tubulature,  or  opening, 
at  the  bottom,  b,  Fig.  98.  This  is  to  be  closed  by  a  stopper  having 
a  short  piece  of  glass  tubing,  over  which  is  slipped  the  rubber 
tube  connecting  the  two  bottles.  A  better  form  of  aspirator  bottle 
has  the  tubulature  drawn  out  so  that  the  rubber  tubing  may  be 
attached  directly  over  this,  c,  Fig.  98. 

An  aspirator  bottle  may  be  made  by  boring  a  hole  in  an  acid 
bottle,  near  the  bottom,  with  a  file  dipped  in  turpentine,  and  then 
slipping  into  this  hole  a  bit  of  glass  tube  covered  with  about  an 
inch  or  so  of  soft  thick  walled  rubber  tubing. 

Aspirators  made  of  zinc,  japanned  and  mounted  so  that  con- 
tinuous suction  can  be  obtained  for  a  long  time  without  changing 
the  connections,  may  be  purchased.  The  small  filter  pumps  de- 
scribed in  Chapter  III.  may  be  used  for  suction,  or  the  blast  de- 
scribed in  Chapter  VI.  for  forcing  air  throug  an  apparatus.  If 
the  pressure  created  by  the  latter  is  too  great,  the  little  regulator 
described  blow  may  be  used.  This,  Fig.  99,  consists  of  a  cylinder 
or  bottle  stoppered  with  a  2-hole  cork  or  rubber  stopper.  One 
of  the  holes  is  left  open  and  through  the  other  passes  a  T-tube, 


I2O 


SMALL  -  CHEMICAL    LABORATORIES. 


one  end  of  which  dips  into  a  little  mercury  in  the  bottle.  The 
pressure  of  the  gas  is  regulated  by  the  distance  into  the  mercury 
which  the  T-tube  dips.  Rubber  tubes  on  which  are  Hoffman 


b 


a. 


Fig.  98.— Aspirators. 


clamps  should  be  used  to  connect  the  upper  branches  of  the  T- 
tube,  one  with  the  blower  and  the  other  with  the  apparatus 
through  which  air  is  to  be  forced. 


MISCELLANEOUS  EQUIPMENT. 


121 


Barometers. — These  may  be  obtained  in  a  variety  of  forms, 
costing  from  $10.00  up.  The  simple  Bunsen's  siphon  barometer, 
consisting  of  a  tube  of  mercury,  the  upper  end  of  which  is  closed 
and  the  lower  is  bent  to  form  a  U  and  left  open,  is  well  suited  to 
laboratory  purposes,  for  gas  analysis,  etc.  The  tube  is  graduated 
into  millimeters  and  is  mounted  on  a  board,  so  that  it  may  be  con- 
veniently hung  up.  These  siphon  barometers  may  be  obtained 
either  filled  with  mercury  or  unfilled.  If  the  former  they  are  liable 
to  break  in  transit,  but  they  are  also  very  troublesome  to  fill. 
Aneroid  barometers  are  unsuited  to  laboratory  use.  A  barometer 
to  be  used  for  gas  analyses,  etc.,  should  preferably  be  graduated 
into  millimeters,  as  nearly  all  tables,  etc.,  are  constructed  to  use 
this  unit  pressure. 


Fig.   9'J.  —  - 


Regulator. 


Beakers.  —  The  best  beakers  are  made  of  what  is  known  as 
'  'trade-mark  glass."  That  is,  the  maker's  name  is  indelibly  stamped 
upon  them.  For  analytical  purposes,  the  lipped  beakers  are  to  be 
preferred  and  for  most  determinations,  the  Griffin's,  or  low  form, 
is  used.  Tall  beakers  are  useful  for  hydrogen  sulphide  precipita- 
tions. Of  the  trade-mark  glasses  the  "Jena"  comes  from  Schott 
and  Gen.  Jena  ;  the  "Nonsol"  from  Whitall,  Tatum  &  Co.,  Phila- 
delphia; the  "Baloc"  from  Bausch  &  Lomb  Optical  Co.,  and  the 
"Kavalier"  from  Joseph  Kavalier.  "Bohemian  Glass"  really 
means  very  little  and  tests  have  shown  it  to  be  no  better  than 
some  of  our  less  pretentious  domestic  glasses. 

Unfortunately  dealers  in  chemical  glassware  do  not  adopt  a 
uniform  system  of  numbering  their  beakers.  Herewith  will  be 


122  SMALL    CHEMICAL    LABORATORIES. 

found  a  table  giving  the  number  and  capacities  in  cubic  centi- 
meters of  various  makes  of  Griffin's  form  beakers : 

Make.      No.  oooo    ooo  oo  o        i        23  4        5 

cc.      cc.  cc.  cc.      cc.      cc.      cc.  cc.      cc. 

Baloc   20      50  100     150    200    350  500    750 

Jena   50  100     150    250    400  600    800 

Kavalier   15       30  50       75     120     200  300    450 

Nonsol1 30      60      75  120     180    250    400  600    750 

6          7          8  9         10        ii  12 

cc.        cc.  cc.  cc.        cc.        cc.  cc. 

Baloc   1000     1500      200  2500    3000    4000  5000 

Jena 1000     1300 

Kavalier   ....   650      900  noo  1800     2400     3000  4000 

Nonsol looo 

Carboys. — These  are  used  in  laboratories  for  the  storage  of 
solutions,  and  acids,  ammonia,  etc.,  are  received  in  them.  The 
problem  with  them  is  usually  how  to  get  the  contents  out  of  them. 
One  of  the  easiest  ways  is  to  place  the  carboy  in  a  Stevenson's 
tilter.  This  consists  of  a  pair  of  rockers  so  fixed  that  the  carboy 
can  be  readily  tilted  on  its  side.  They  can  be  easily  attached  and 
removed  from  the  carboy.  Another  simple  way  of  drawing  from 
a  carboy  is  to  set  the  carboy  on  a  brick  or  block  a  foot  or  so  from 
the  floor  and  draw  the  contents  by  means  of  a  siphon.  A  pump 
may  be  purchased  or  made  for  emptying  carboys,  consisting  of  a 
large  rubber  stopper  perforated  with  two  holes,  through  one  of 
which  passes  a  tube  long  enough  to  reach  to  the  bottom  of  the 
carboy  and  having  its  upper  end  bent  into  a  wide  U,  so  as  to  de- 
liver the  liquid  into  a  bottle  or  beaker.  Through  the  other  hole 
of  the  stopper  a  short  piece  of  tubing  reaches  just  inside  and  is 
connected  with  an  ordinary  bicycle  foot  pump.  The  rubber  stop- 
per is  now  forced  into  the  mouth  of  the  carboy  and  wired  or  tied 
securely  in.  The  acid  is  then  forced  out  by  working  the  pump. 
The  bought  apparatus  has  a  special  form  of  clamp  to  keep  the 
stopper  in  the  bottle  when  the  pressure  in  the  latter  gets  up  to 
the  point  of  forcing  the  acid  out. 

For  agitating  the  contents  of  the  carboy,  as  in  making  solu- 
tions in  large  quantities,  blowing  compressed  air  through  the 
liquid  by  means  of  a  long  tube  reaching  to  the  bottom  of  the 

Wonsol   Beakers   No.    OA  contain    150   cc,  2  A,  300  cc.  and  3  A,  500  cc. 


MISCELLANEOUS  EQUIPMENT.  123 

carboy  will  prove  convenient  and  efficient.  Where  air  would 
oxidize,  carbon  dioxide  or  hydrogen  may  be  generated  in  stone 
jugs,  washed  and  passed  through. 

Casseroles. — These  are  nothing  more  than  evaporating  dishes 
with  flat  bottoms  and  handles  to  the  side.  They  are  made  of  both 
Royal  Berlin  and  cheaper  porcelains,  and  in  sizes  to  contain  from 
30  to  2000  cc.  They  are  usually  used  with  porcelain  handles, 
though  some  forms  have  wooden  handles  and  are  also  provided 
with  covers.  Porcelain  casseroles  are  much  used  in  iron  and  steel 
laboratories.  They  are  open  to  the  same  objections  as  are  held 
against  porcelain  dishes  (see  dishes).  They  are  much  less  fragile 
than  beakers  and  hence  are  well  suited  to  the  rough  usage  of 


(L 


Fig.  100.— Clamps. 

laboratories  where  many  determinations  are  made  in  a  short 
time.  They  may  be  removed  from  the  hot  plate  or  sand  bath  after 
the  handles  become  hot  by  slipping  over  the  latter,  just  before  re- 
moval, a  piece  of  large  bore  rubber  tubing,  large  enough  to  go  on 
and  off  without  friction.  Precipitates  may  be  rubbed  out  of  them 
easiest  with  a  rubber  finger  cot  drawn  over  the  fore-finger. 

Clamps. — These  are  shown  in  Fig.  100.  Forms  a  and  b  are 
used  for  burettes  and  other  thin  tubular  apparatus.  Form  a  will 
hold  the  burette  only  parallel  with  the  rod  of  the  support.  The 
jaws  being  closed  wth  a  spring,  it  is  an  easy  matter  to  unclamp 
anything  from  them.  The  form  b  will  hold  the  tube  at  any  angle 
to  the  rod  of  the  support,  and  is  an  excellent  clamp  for  general 


I24  SMALL    CHEMICAL    LABORATORIES. 

laboratory  use,  for  this  reason.  Clamp  e  is  intended  to  screw 
into  a  wall  or  desk  and  is  so  constructed  that  the  graduated  part 
of  the  burette  is  not  covered.  All  of  the  above  clamps  hold  the 
burette  or  tube  at  a  fixed  distance  from  the  rod  of  the  support. 
The  clamp  c  will  allow  the  rod  to  be  held  at  any  distance  up  to 
5  or  6  inches.  It  is  attached  to  the  support  rod  by  the  clamp  d. 
This  latter  clamp  may  be  obtained  with  a  swivel  in  the  middle, 
controlled  by  a  thumb  nut  and  with  this  the  clamp  may  be  at- 
tached to  the  rod  at  any  angle.  Large  clamps,  similar  to  c,  with 
grips  adaptable  to  irregular  shapes,  may  be  obtained  for  holding 
tubes  over  one  inch  in  diameter. 

If  the  jaws  of  the  clamps  are  not  provided  with  cork  grips,  a 
piece  of  felt  should  be  glued  in  them  in  order  to  give  them  a 
securer  hold  on  glass  apparatus.  Hoffman  clamps  and  pinch  cocks 
are  described  under  rubber  tubing. 

Condensers. — Every  catalogue  of  chemical  apparatus  will  de- 
scribe many  forms  of  these.  Condensers  which  are  intended  to 
condense  the  vapors  and  drop  the  liquid  back  into  the  flask  in 
which  the  boiling  is  taking  place  are  called  "reflex"  condensers. 
The  simplest  form  of  condenser  is  Liebig's.  a,  Fig.  101,  shows 
a  simple  Liebig's  condenser  which  may  be  made  by  any  one  who 
is  at  all  proficient  in  glass  blowing,  and  b,  Fig.  101,  shows  a  con- 
denser which  may  be  made  from  a  large  piece  of  glass  tubing  or 
even  a  student's  lamp  chimney.  The  construction  of  both  are 
evident. 

The  end  of  the  condenser  in  the  boiling  flask  should  be 
ground  to  a  V-shaped  point,  as  shown  in  Fig  101,  in  order  to  fa- 
cilitate the  return  of  the  liquid  to  the  flask  or  retort.  The  cold 
water  should  always  enter  at  the  end  of  the  condenser  furthest 
from  the  retort.  In  starting  a  reflex  condenser,  it  may  be  neces- 
sary to  reverse  this  arrangement,  for  a  second,  by  turning  the 
condenser  upside  down,  in  order  to  work  out  the  air. 

Dishes. — These  may  be  obtained  from  dealers  in  chemical  ap- 
paratus, made  of  porcelain,  glass,  platinum,  nickel,  iron,  silver, 
lead,  copper,  etc.  For  analytical  purposes  dishes  of  porcelain  and 
platinum  are  usually  used  and  sometimes  dishes  of  glass  and 
silver. 

Porcelain  dishes  are  much  used  in  analytical  laboratories  for 
silica  determinations.  In  spite  of  this  fact,  they  are  untrustworthy, 
owing  to  the  fact  that  it  is  almost  an  impossibility  to  remove  all 


MISCELLANEOUS  EQUIPMENT. 


125 


the  silica  from  them.  When  silica  is  determined  in  steel  and  iron 
by  Drown's  method,  they  probably  give  good  results,  but  for 
silica  in  slag,  clay,  etc.,  there  is  usually  a  milligram  or  so  which 
no  amount  of  rubbing  will  remove  from  the  dish.  The  first  cost 
of  platinum  dishes  is,  of  course,  high,  but  all  the  silica  can  be  re- 
moved from  them  and  they  are  practically  indestructible,  so  that 
the  increased  accuracy  and  the  breakage  of  porcelain  dishes  very 
soon  amounts  to  more  than  the  interest  and  depreciation  on  the 
platinum  ones.  I  have  used  dishes  of  Nonsol  glass  and  found  them 
preferable  to  porcelain  dishes  for  silicate  work.  If  platinum  is 
used,  however,  the  work  is  unquestionably  more  accurate,  and 


Fig.  101. — Condensers. 

owing  .to  the  fact  that  metal  is  a  good  conductor  of  heat,  solutions 
in  them  evaporate  much  faster. 

To  clean  precipitates  out  of  dishes,  a  rubber  finger  cot  will 
be  found  convenient.  This  is  slipped  over  the  index  finger  and 
the  dish  rubbed  hard.  If  glass  dishes  are  used,  the  completeness 
of  the  removal  of  silica  may  be  tested  by  rinsing  the  dish  with 
hot  water,  when  it  will  dry  almost  at  once,  and  the  silica  may  be 
readily  seen  and  removed  by  vigorous  dry  rubbing  with  a  small 
piece  of  ashless  filter  paper.  This  latter  is  then  incinerated  with 
the  main  body  of  the  silica. 

Flasks. — These  may  be  obtained  in  some  fifteen  or  twenty 
different  forms,  of  which  the  Erlenmeyer  and  the  globe  are  most 
used  in  analytical  laboratories.  The  Erlenmeyer  is  shown  in  a, 


126 


SMALL    CHEMICAL    LABORATORIES. 


Fig.  1 02.  It  is  an  excellent  flask  in  which  to  filter  by  suction  (see 
Chapter  III.),  for  titrations,  where  precipitates  are  to  be  formed  in 
a  flask  by  shaking,  etc.,  and  from  which  to  filter  by  decantation. 
Flasks  to  be  used  with  suction  should  be  heavy  enough  to  stand 
heavy  pressure.  A  very  heavy  Erlenmeyer  with  a  side  neck  is 
made  especially  for  this  purpose.  For  most  work  an  Erlenmeyer 
with  a  rather  wide  mouth  will  be  found  convenient.  These  flasks 
are  made  as  large  as  i  gallon  and  as  small  as  I  ounce  capacity 
and  can  be  obtained  up  to  32  ounces  with  ground  glass  stoppers, 
or  with  a  pour  out. 

Globe  flasks,  b,  Fig.  102,  are  made  in  sizes  ranging  from  y2 
ounce  to  5  gallons,  and  with  round  or  flat  bottoms.  When  they 
are  to  bear  corking  they  shauld  have  what  is  known  as  ring- 


a 


d 


Fig.   102.— Flasks. 


finish  necks,  that- is,  a  heavy  ring  of  glass  around  the  neck,  as 
shown  in  b.  The  inside  edge  of  the  ring  should  also  be  ground 
off  to  prevent  cutting  of  the  stopper.  When  the  flask  does  not 
have  to  be  corked  a  vial  mouth  may  be  used,  c,  Fig.  102.  For 
wash  bottles  (Chapter  V.)  the  ring-finish,  flat-bottomed  flask 
should  be  used. 

A  small  conical  flask  having  a  ring  around  its  upper  end 
and  known  as  an  "assay  flask"  or  "matrass,"  e,  Fig.  102,  is  used 
in  parting  gold  bullion.  A  round  bottom  flask,  d,  Fig.  102,  with  a 
long  neck,  made  of  hard  Bohemian  glass,  is  used  for  nitrogen 
determinations  by  Kjehldahl's  method.  Globe  flasks,  both  with  flat 
and  round  bottoms,  having  side  necks,  are  used  in  making  boiling 
point  determinations  and  also  for  determining  substances  by 
evolution  and  distillation  methods. 


MISCELLANEOUS  EQUIPMENT. 


127 


Any  of  the  foregoing  flasks  may  be  obtained  made  of  any 
glass  desired,  Kavalier's,  Bohemian,  Baloc,  Nonsol,  Jena,  etc. 
(see  Beakers). 

G-ases,  Drying  and  Absorbing. — For  this  purpose  U-tubes, 
potash  bulbs,  calcium  chloride  tubes  and  calcium  chloride  jars 
are  used.  U-tubes,  Fig.  103,  are  made  in  a  number  of  forms  and 
are  suited  to  drying  gases  by  the  use  of  calcium  chloride,  an- 
hydrous copper  sulphate,  sulphuric  acid,  etc.  Figs,  a  103  and 
b  103  are  good  forms  where  the  gas  has  merely  to  be  dried  or 
purified  and  the  form  shown  in  Fig  c  103,  with  glass-stoppers,  is 
to  be  preferred  where  the  gas  has  to  be  caught  and  weighed.  The 
other  forms  can  also  be  used  for  this  purpose.  In  this  case,  the 
tubes  should  be  capped  when  they  are  not  connected  in  the  train 


a 


d 

Fig.   103.— U-Tubes. 


C 


by  means  of  small  pieces  of  thin  walled  rubber  tubing,  one  end 
of  which  are  closed  by  bits  of  glass  rod  or,  better  still,  capillary 
glass  tubing.  To  suspend  tubes  to  be  weighed,  use  fine  platinum 
wire.  U-tubes,  in  which  liquids  are  to  be  used,  should  be  filled 
with  glass  bead's  or  cracked  up  pumice-stone,  and  should  contain 
only  sufficient  liquid  to  cover  the  bend.  Where  dry  substances  are 
used,  plugs  of  loose  absorbent  cotton  should  be  placed  on  top  of 
this,  in  both  branches  of  the  tube,  to  prevent  fine  particles  from 
being  carried  out  of  the  tube.  Where  tubes  are  stoppered  with 
corks  the  ends  containing  these  should  be  dipped  in  melted  para- 
ffin or  wax,  so  that  all  the  cork  and  some  of  the  end  is  covered 
to  prevent  escape  of  the  gas. 

Calcium  chloride  tubes  are  shown  in  a  and  b,  Fig.  104.   They 
may  be  obtained  either  with  one  or  two  bulbs.    The  form  shown 


128 


SMALL    CHEMICAL    LABORATORIES. 


in  b,  Fig.  104,  has  a  small  tube  extending  into  the  bulb  and  is  in- 
tended to  catch  some  moisture  (as  water)  by  condensation  in  the 
first  bulb,  and  so  save  the  calcium  chloride.  These  tubes  are  sel- 
dom weighed  and  are  usually  used  as  guard  tubes.  The  calcium 
chloride  jar  is  shown  in  Fig.  104  c.  It  is  never  weighed  and  is 
usually  used  only  to  purify  or  dry  air  or  gases.  A  small  pad  of 
asbestos  fibre  or  cotton  is  placed  at  the  constricted  point  just 
above  the  tubulature  and  the  purifying  substance  on  this.  They 
may  also  be  used  for  liquids  by  filling  the  upper  portion  with  glass 
leads  and  drenching  these  with  the  liquid.  They  may  be  used  for 
both  liquids  and  solids  by  having  the  lower  part  of  the  tube  filled 
with  liquid  nearly  to  the  tubulature  and  having  the  tube  by  which 


Fig.   104. — Calcium  Chloride  Tubes  and  Jars. 

the  gas  enters  bent  so  that  the  latter  will  have  to  bubble  through 
this.  Fig.  104,  d,  shows  a  very  powerful  purifying  apparatus  made 
from  a  calcium  chloride  jar  and  a  long  narrow  test  tube.  The 
lower  part  is  filled  with  sulphuric  acid  (caustic  potash  for  CO2) 
and  the  upper  part  and  test  tube  with  calcium  chloride  (soda  lime 
for  CO2).  The  test  tube  rests  on  a  plug  of  loose  cotton  and  the 
gas  is  led  out  of  the  apparatus  by  means  of  the  tube  as  shown. 
In  this  apparatus,  the  gas  has  to  travel  the  entire  length  of  the 
jar  and  also  the  test  tube,  as  shown  by  the  arrows. 

Potash  bulbs  are  for  use  with  liquids  only,  though  there  is 
usually  attached  to  them  when  they  are  to  be  weighed  a  tube  con- 
taining calcium  chloride  or  soda  lime.  The  most  common  forms 


MISCELLANEOUS  EQUIPMENT.  129 

are  shown  in  Fig.  105.  Where  the  bulb  is  to  be  weighed  the  form 
marked  b  is  best  suited,  or  the  form  a  may  be  weighed  together 
with  a  U-tube  for  a  guard.  When  not  connected  up  in  the  train 
they  should  be  capped  as  directed  for  U-tubes.  To  fill  the  bulbs, 
attach  a  short  piece  of  rubber  tubing  to  one  end  and  dip  the  other 
in  the  solution  held  in  a  small  shallow  dish.  Apply  suction  to  the 
rubber  tubing  with  the  mouth  until  the  bulbs  are  filled  to  the 
proper  height.  Then  wipe  the  tube  dry  inside  and  out  with  pieces 
of  filter  paper  or  a  soft  cloth. 

Gas  may  also  be  purified  by  allowing  it  to  bubble  through 
solutions  held  in  4-ounce  bottles. 

Gas  Generators. — There  are  many  forms  of  these,  and  to  de- 


a  d 

Fig.    105.— Potash    Bulbs. 

scribe  them  would  of  itself  fill  a  volume.  A  simple  generator  for 
hydrogen  sulphide,  carbon  dioxide  or  hydrogen  is  shown  in  Fig. 
106.  The  acid  is  held  in  the  bottle,  A,  which  is  provided  with  a 
tubulature.  The  iron  sulphide,  etc.,  is  in  the  calcium  chloride  jar, 
B.  The  acid  flow  is  regulated  by  a  Mohr's  clamp,  a,  and  trickling 
through  the  sulphide  generates  the  gas.  The  spent  acid  falls  into 
the  lower  part  of  the  jar  and  is  sucked  off  into  a  waste  bottle  by 
the  siphon,  D.  The  gas  is  washed  by  bubbling  through  water  in 
E  and  its  flow  is  controlled  by  the  Mohr's  clamp,  e. 

Hydrometers. — These  are  used  for  taking  the  specific  gravity 
of  liquids.  Some  of  them  are  very  accurate,  reading  to  the  third 
and  fourth  decimal  place.  For  milk,  wine,  oils,  etc.,  special  hydro- 
meters are  employed  and  they  will  be  found  listed  in  the  cata- 
logues of  the  various  dealers  in  chemical  supplies.  For  ordinary 


1 3o 


SMALL   CHEMICAL   LABORATORIES. 


laboratory  work  two  hydrometers  will  be  found  useful:  One  for 
taking  the  specific  gravity  of  liquids  heavier  than  water  and  one 
for  use  with  those  lighter.  Since  temperature  affects  specific 
gravity,  hydrometers  having  thermometers  blown  in  them  are  to 
be  preferred,  as  temperature  and  density  can  be  read  at  the  same 
time.  Universal  hydrometers  are  also  made  for  use  with  liquids 
either  lighter  or  heavier  than  water.  Very  delicate  hydrometers 
usually  have  but  a  small  range  and  hence  are  usually  purchased 
in  sets.  Hydrometers  reading  in  degrees  Baume,  Brix,  Balling, 


rt 


Fig.    106.— Gas   Generator. 

etc.,  instead  of  specific  gravity  compared  with  water  are  also  used. 
Hydrometer  jars  are  tall  narrow  cylinders,  mounted  on  a  foot,  in 
which  to  float  hydrometers.  The  Westphal  Balance  is  also  used 
to  take  the  specific  gravity  of  liquids  and  is  very  convenient  and 
accurate. 

For  taking  the  specific  gravity  of  both  solids  and  liquids, 
small  bottles  having  narrow  holes  drilled  through  the  stoppers  to 
enable  the  operator  to  fill  them  precisely,  are  used.  They  are 
called  specific  gravity  bottles  or  pycnometers.  Fig.  107  shows 


MISCELLANEOUS  EQUIPMENT.  13 i 

the  forms  most  commonly  used,  of  which  a  and  b  are  the  cheapest, 
and  c  is  the  best,  while  d  and  e  (Sprengel's  tubes)  are  used  for 
taking  the  specific  gravity  of  liquids  where  only  a  small  amount 
is  available.  The  tube  shown  with  the  latter  two  forms  is  used 
to  fill  them. 

Measuring  Apparatus.— The  chief  forms  of  these  are  burettes, 
pipettes,  graduated  flasks,  graduated  cylinders  and  "graduates." 
Burettes  have  already  been  described,  and  an  automatic  pipette 
was  also  mentioned,  both  in  Chapter  VII. 

For  roughly  measuring  reagents,  graduated  cylinders  are 
usually  used.  These  may  be  obtained  in  sizes  ranging  from  5  cc. 


\J 


Fig.  107.— Specific  Gravity  Bottles. 

to  several  liters.  A  convenient  form  is  manufactured  by  Whitall, 
Tatum  &  Co.,  in  which  the  foot  is  made  very  heavy  in  order  to 
make  the  cylinder  less  liable  to  turn  over.  Cylinders  can  be  OD- 
tained  with  double  graduations  and  also  with  ground  glass  stop- 
pers. The  latter  form  are  handy  for  making  up  dilute  acids  and 
solutions  in  which  two  liquids  are  used. 

For  accurately  delivering  small  volumes  of  solutions,  pipettes 
are  used.  These  are  made  in  sizes  ranging  from  5  to  100  cc. 
and  are  filled,  to  a  given  mark  on  the  stem  above  the  bulb,  with 
the  liquid  by  suction  and  then  allowed  to  empty  and  drain  them- 
selves. Graduated  pipettes,  which  are  practically  nothing  but  small 


132  SMALL    CHEMICAL    LABORATORIES. 

burettes,  the  flow  out  of  which  is  controlled  by  the  finger  on  the 
upper  end,  can  also  be  obtained  and  with  these  any  volume  can  be 
delivered.  They  are  made  as  small  as  I  cc.,  graduated  into  i/ioo 
cc.,  and  as  large  as  50  cc.,  graduated  into  i/io  cc.  Special  pipettes 
are  also  made.  Some  bulb  pipettes  are  made  to  deliver  a  certain 
volume  between  a  mark  on  the  upper  stem  and  one  on  the  lower. 
Pipettes  are  usually  marked  to  show  at  which  temperature  the 
given  volume  is  delivered. 

Graduated  flasks  or  "Volumetric  Flasks"  are  usually  made  to 
hold  a  certain  volume  when  filled  to  a  given  mark  on  the  neck, 
although  they  can  be  obtained  with  two  marks,  the  lower  of  which 
denotes  the  volume  contained  and  the  upper  the  volume  delivered. 
Flasks  for  volumetric  work  should  preferably  have  ground  glass 
stoppers.  The  sizes  kept  in  stock  by  dealers  in  chemical  glass- 
ware are  from  25  cc.  to  2  liters. 

Measuring  apparatus  may  now  be  obtained  accompanied  by 
certificates  of  the  U.'S.  Bureau  of  Standards  as  to  correct  volume, 
or  it  may  be  sent  to  them  for  verification. 

Motors. — For  laboratory  purposes  electric  and  water  motors 
will  be  found  most  convenient  for  furnishing  power.  A  small  J4 
H.P.  motor  will  run  almost  any  piece  of  machinery  about  an  ana- 
lytical laboratory  and  these  may  be  purchased  for  between  $40.00 
and  $50.00,  wound  for  no-volt  or  22O-volt  circuit.  For  running 
crushing  and  grinding  machinery,  a  I  H.P.  motor  will  usually  be 
sufficient  and  this  can  be  obtained  for  about  $75.00.  For  running 
a  few  stirrers,  rotating  anodes,  etc.,  a  No.  7  Porter  motor  wound 
either  for  battery  ($7.00)  or  power  ($8.00)  may  be  used  to  ad- 
vantage, a  leather  shoe-string  serving  for  a  belt. 

Rabe's  small  water  motors  are  also  useful  for  running  a  stir- 
rer  or  two.  They  cost  $6.75  with  holder  to  attach  them  to  a  sup- 
port. Connections  are  made  to  water  faucets  with  stout  rubber 
tubing.  Larger  water  motors,  the  power  of  which  will  of  course 
depend  on  the  water  pressure,  are  obtainable,  in  sizes  ranging 
from  i/io  to  4  or  more  horse  power.  If  good  water  pressure  is 
at  hand  they  are  cheaper  than  electric  motors. 

Where  neither  electricity  nor  gas  are  obtainable  hot  air  mo- 
tors may  be  used.  They  are  very  expensive,  however,  a  1/5  H.  P. 
motor  costing  about  $300. 

Rubber  Stoppers,— These  should  be  of  the  purest  gum  and 


MISCELLANEOUS  EQUIPMENT. 


133 


can  be  obtained  solid  or  perforated  with  one,  two  or  even  three 
holes.    They  are  made  in  the  following  sizes: 

Diametei 
of  Top. 
Size.  mm. 
oo      .14 

0  17 

1  18 

2  2O 

3  23 

4  25 

5  27 

6  32 

To  push  glass  tubing  through  the  perforations  of  rubber 
stoppers,  first  round  the  end  of  the  tube  with  a  file,  or  by  heat, 


ter         Diameter 

Diameter 

Diameter 

p.         of  Bottom. 

of  Top. 

of  Bottom. 

ins. 

mm. 

ins. 

Size. 

mm. 

ins. 

mm. 

ins. 

0-55 

10 

0-39 

7 

37 

1.46 

30 

1.18 

0.67 

12 

0.47 

8 

41 

1.61 

33 

1.30 

0.71 

15 

0-59 

9 

45 

1.77 

37 

1.46 

0.79 

16.5 

0.65 

10 

50 

1.97 

42 

1.65 

0.91 

18 

0.71 

ii 

56 

2.  2O 

50 

1.97 

0.98 

20 

0.79 

12 

65 

2.56 

59 

2.32 

1.  06 

23 

0.91 

13 

7° 

2.76 

60 

2.36 

1.26 

26 

1.02 

a. 


b 


c 


d 


Fig.   108.— Hoffman's  Clamps  and  Mohr's  Pinch  Cocks. 

and,  after  cooling,  moisten  the  rod  and  hole.  Water  acts  as  a  lub- 
ricant between  rubber  and  glass.' 

Rubber  Tubing. — Rubber  tubing  for  connecting  burners  to 
gas  taps  should  be  heavy  walled  with  so-called  "cloth  impression" 
tubing  of  about  6  to  8  mm.  04  inch)  internal  diameter  and  hav- 
ing walls  3  to  4  mm.  thick.  Tubing  of  this  size  may  also  be  used 
for  filtering  by  suction. 

For  connecting  up  glass  apparatus  and  for  general  laboratory 
use,  a  tubing  of  pure  black  or  red  gum  should  be  used.  It  should 
be  seamless  and  may  be  obtained  either  with  thick  or  thin  walls 
and  in  sizes  ranging  from  3  to  18  mm.  internal  diameter.  In  my 
own  laboratory,  I  use  red  rubber  tubing  with  thick  walls  and  find 
3  mm.,  5  mm.,  6  mm.,  and  9  mm.  good  sizes  to  keep  on  hand. 


134 


SMALL    CHEMICAL    LABORATORIES 


For  controlling  the  flow  of  liquids  and  gases  through  rubber 
tubing,  Hoffman's  clamps,  c  and  d,  Fig.  108,  and  Mohr's  pinch 
cocks,  a  and  b,  Fig.  108,  are  used.  With  the  former  the  flow  can 
be  regulated,  but  the  latter  is  intended  only  to  shut  off  the  flow 


100.— Blair's    Mechanical    Stirrer. 


Fig.   110.— Dudley's  Mechanical   Shaker. 

suddenly.  Improved  forms  of  Hoffman's  clamps  are  now  made 
which  can  be  attached  to  tubing  without  disconnecting  the  latter, 
Fig.  108,  c. 

Stirrers,  Shakers,  Etc. — A  great  variety  of  mechanical  con- 


MISCELLANEOUS  EQUIPMENT. 


135 


trivances  for  stirring  liquids  are  on  the  market,  of  which  Fig. 
109  shows  one  of  the  simplest,  devised  by  Blair,  and  illustrated 
in  his  "Chemical  Analysis  of  Iron."  It  may  now  be  purchased  of 
dealers  in  chemical  supplies. 

A  simple  shaker  for  precipitation  is  Dudley's,  shown  in  Fig. 
no,  and  this  also  is  a  stock  article..  Numerous  forms  of  shaking 
devices  are  illustrated  and  described  in  various  text  books  of 
analytical  chemistry. 

Mr.  Robert  Job  described1  a  simple  method  for  agitating 
solutions  by  means  of  air  blown  through  them.  The  air  is  first 


Fig.    111.— Job's   Air   Agitator. 

made  to  bubble  through  water  to  take  out  the  dust,  etc.,  and 
is  then  passed  into  the  solution  through  a  glass  tube.  For  dis- 
solving steel  in  cupric  chloride  solution,  Mr.  Job  placed  the  drill- 
ings in  a  test  glass.  Fig.  in  shows  the  apparatus.  For  phos- 
phorous determinations  Erlenmeyer  flasks  were  used  and  for 
magnesia  precipitates  the  author  has  used  beakers. 

Thermometers. — For  ordinary  purposes,  chemical  thermo- 
meters having  a  long  thin  stem,  about  ^4-inch  bore,  and  the  scale 
engraved  on  the  glass,  will  answer.  They  can  be  obtained  read- 


'Chemical    Engineer,    II.,    S.'.'J. 


1 36  SMALL    CHEMICAL    LABORATORIES. 

ing  as  high  as  360°  C,  graduated  into  degrees,  or  reading  to 
550°  C.  graduated  every  5  degrees.  For  calorimeters  and  such 
work  more  delicate  thermometers  can  be  obtained,  while  for  re- 
search work  in  boiling  and  melting  points  Beckmann's  thermo- 
meters are  used.  Thermometers  accompanied  by  certificates  as 
to  their  accuracy  from  the  Deutsche  Physikalische-Technische 
Reischsanstalt  or  the  U.  S.  Bureau  of  Standards  can  be  obtained 
at  a  slightly  increased  cost. 

Pyrometers  are  used  for  temperatures  higher  than  550°  C. 
Of  these  Le  Chatelier's,  Wanner's,  the  Fery  and  Bristol's  are  all 
good  forms,  each  one  of  which  is  best  suited  to  some  particular 
kind  of  work.  They  are  fully  described  in  various  works  on 
metallurgy,  thermochemistry,  etc. 


INDEX 


Page. 

Abbe   jar  mill 101 

Acetylene    for    laboratory    purposes.     64 

Air    baths     67 

temperature    regulator    for 67 

Air   blast  for   blast  lamps,   etc 31 

Agate    mortar    95 

Agitator,    Job's    air 135 

Ammeter     83 

Anodes    for    electrochemical    analy- 
sis      80,     84 

Aspirators     119 

Aspirator   bottles    119 

Assay  balance    52 

Assay    furnaces     102 

coal   fired    112 

gas  fired    103 

gasolene   fired 108 

Assay  furnace  tools,    etc 116 

Assay    laboratory 6 

Arrangement   of   the    laboratory....       1 

Balances,     analytical 50 

assay    52 

for  rough  weighing 53 

Balance  pans   54 

support     46 

Barometer     121 

Batteries,     primary    electric 70 

secondary    or    storage 7s 

Beakers     121 

Bell-jar  and   plate   for   filtration   by 

suction     17 

Bench,    laboratory    50 

Blair's   mechanical   stirrer 134 

Blast  lamps    30 

Bunsen  burners 65 

Burners     65 

Burettes     38 

appliances  to  aid  in  reading.  ..  41 

automatic    zero    point 40 

caps    for    41 

frame   support   for 37 

portable   stand  for 42 

table   for    37 

Calcium    chloride    jar 138 

tubes   137 

Carboys     122 

agitating   contents    of 122 

emptying     122 

Casseroles    123 

Cathodes  for  electrochemical   analy- 
sis     80,  84 

Ceiling  of  the   chemical   laboratory.  3 

Chapman's  vacuum  pump 15 

Chilled  iron  plate  and  pestle 90 

Clamps    123,  134 

Hoffman's     134 

Concrete  top  for  tables,  hood,  etc..  8 

Condensers    124 


Page. 
Condenser    for    preparing    distilled 

water  from  waste  steam..  70 

Constant  level  for  water  baths 67 

Crucibles,   fire   clay 116 

Gooch     17,  35 

platinum    33 

porcelain    35 

Crucible    supports    29 

tongs    35 

Crushers    §9 

Blake's     ','.',  68 

Bosworth's     68 

Braun's    "Lightning"     94 

Calkins'    "Agrance"    93 

Case    ic; 

Gates'      94 

Taylor's    hand 91 

Weatherhead's    92 

Cupboards    below    desks,    etc 23 

Cupels    H6 

Cupel    machines    117 

Cylinders,    graduated    131 

Dangler's  gasolene   lamp 56 

Desiccators     36 

Desks,     laboratory     20 

with   projecting   drawers    22 

Disc  pulverizer,  Braun's 98 

Calkins'     ii'.i 

Dishes     124 

Distilled   water,   containers   for 72 

preparation    of    69 

Drawers   for   desks,    etc 21 

Drying  board  for  apparatus 13 

Dudley's    mechanical    shaker 134 

Electric    batteries,    primary 76 

secondary    or     storage 78 

Electric  lighting  current  for  electro- 
chemical   analysis    73 

Electrodes    for    electrochemical    an- 
alysis       80 

Electrochemical   analysis,    apparatus 

for     73 

Extraction   apparatus    IS 

Filter    stands     27 

Filtration  by  vacuum 14 

Filtration,    table   for   rapid 26 

funnels    for    rapid 28 

Fire  hose    19 

Flasks     125 

Floor  of  the  laboratory 2 

Funnels   for   rapid  filtrations 28 

Gas,    acetylene    65 

gasolene    56 

machines  for  generating  gaso- 
lene       61 

drying  and  absorbing  apparatus  127 

generators     129 

tap?     9 


INDEX. 


Page. 

Gasolene   gas 56 

lamp     56 

stoves    58 

gas  machines 61 

Gooch  crucible   17,     35 

Gould's     air     pressure     or     vacuum 

pump     32 

Guide  for  drawers   21 

Heating   the    laboratory 3 

Hoffman's    clamps    134 

Hoods  7 

canopy    for    10 

concrete    top    for     8 

lighting  of    10 

ventilation    of    10 

Hoskins'    gasolene    lamp 57 

Hot   plates    66 

Ignitions    in    a   muffle    furnace 33 

Ignition   table    29 

Indicator  bottles    44 

Iron    and    steel    analysis,    laboratory 

for   3 

Jar   mill    101 

Jewel  gasolene  lamp  57 

Jewell     still      70 

Jewett's  reagent  bottles   2o 

Job's   air   agitator    135 

Lamps,    gasolene    56 

Lamp  resistance  for  electrochemical 

analysis     73 

Lighting  the   laboratory    2 

Location  of  the  laboratory 2 

McKenna's     mechanically     operated 

agate  mortar  and  pestle.  .     96 
Measuring    apparatus,    volumetric . .   131 
instruments,    for    electric    cur- 
rents        83 

Mohr's    pinch    cock.... 134 

Mortars     86,     93 

Motors,  electrical,  hot  air  and  water  138 

Muffle    furnaces,    coal    fired 112 

gas    fired    105 

gasolene  fired    106 

Muller,  gyratory  97 

Ore    crushers     89 

Pestles     86 

Pinch  cock,   Mohr's 134 

Pipettes     43 

Potash    bulbs    128 

Pressure    regulator    119 

Pulverizers,    sample,    etc 96 


Page. 

Pycnometers     130 

Quartering    samples     89 

Reagent    bottles    24 

Resistance  board  for  use  in   electro- 
chemical   analysis    73 

Rheostat    78 

Rochlitz  automatic  water  still 69 

Rotating  anode    84 

Rubber     stoppers     132 

tubing    133 

Samples,   preparing  for  analysis....     87 
Sampling    appliances     86 

grinders     86 

Sand  baths   66 

S-corifiers     116 

Shaker     mechanical    134 

Shelves     23 

Sieves     88 

Sinks    12 

Sink  table   12 

Specific  gravity   bottles    130 

Spot  plates    44 

Springfield     gas    machine 61 

Stands  for  electrochemical  analysis.     80 
Stills  for  pure  water 69 

nitrogen,   ammonia,   etc 18 

Stirrer,    mechanical    134 

Stoppers,    rubber    132 

Storage  batteries    78 

Stoves    58,      66 

S-tutzer's     nitrogen     still 18 

Thermometers    135 

Thermostat     68 

Titrations,  table  and  apparatus  for.     37 
Triangles    for    supporting   crucibles.     30 

Tubing,   rubber    133 

U-tubes    127 

Vacuum,   use  for  filtering 14 

pumps     14,     32 

Ventilation   of   the    laboratory 2 

Voltmeter      83 

Walls   of   the   laboratory 3 

Wash  bottles,  covering  for  necks  of     28 

Water   bath    66 

constant    level    for 67 

blower    31 

supply    12 

taps    13 

Weighing    bottles     55 

Weights     53 


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"FIELD     SYSTEM" 

By  FRANK  B.  GILBRETH 

This  book. is  written  by  Frank  B.  Gilbreth,  one  of  the  largest  general 
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PORTLAND  CEMENT 

Its  Composition,  Raw  Materials,  Manufacture, 
Testing  and  Analysis 

By  RICHARD  K.  MEADE,  B.  S. 


CHEMIST    TO    THE    DEXTER    PORTLAND    CEMENT    CO. 
EDITOR  OF  "THE  CHEMICAL   ENGINEER" 


CONTENTS 

INTRODUCTION. — Chap.  I — History  of  the  Development  of  the 
American  Portland  Cement  Industry.  II — Chemical  Composition 
of  Portland  Cement. 

MANUFACTURE. — III — Raw  Materials.  IV — Proportioning  the  Raw 
Materials.  V — Quarrying,  Excavating,  Drying  and  Mixing  the 
Raw  Materials.  VI — Grinding  the  Raw  Material  and  Grinding 
Machinery.  VII — Kilns  and  Burning.  VIII — Cooling  and 
Grinding  the  Clinker,  Storing  and  Packing  the  Cement,  Etc. 

ANALYTICAL  METHODS. — IX — The  Analysis  of  Cement.  X — The 
Analysis  of  Cement  Mixtures,  Slurry,  Etc.  XI — The  Analysis  of 
the  Raw  Materials. 

PHYSICAL  TESTING.— XII— The  Inspection  of  Cement.  XIII— Spe- 
cific Gravity.  XIV — Fineness.  XV — Time  of  Setting.  XVI— 
Tensile  Strength.  XVII — Soundness. 

MISCELLANEOUS. — XVIII — The  Detection  of  Adulteration  in  Port- 
land Cement.  XIX — Trial  Burnings.  Appendix — Tables. 

Cloth,    6x9    inches;    385    pages;    100    illustrations;    49    tables. 
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Concrete 

And  Reinforced  Concrete 
Construction 

By  HOMER  A.  REID,  Assoc.  M.  Am.  Soc.  C.  E. 

Assistant  Engineer,  Bureau  of  Buildings,  New  York  City 

906  pages;    715  illustrations  ;    70  tables  ; 
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PRACTICAL    CEMENT 
TESTING 

By  W.  PURVES  TAYLOR,  M.  E.,  C.  E. 

Engineer  in  Chief  of  Philadelphia  Municipal 
Testing   Laboratories 


This  is  the  first  practical  and  exhaustive  treatise  on  this  im- 
portant subject.  It  has  already  been  adopted  as  a  text-book  by 
the  University  of  Pennsylvania  and  leading  technical  schools. 
Each  chapter  contains  a  minute  description  of  the  methods  fol- 
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on  the  interpretation  of  results,  one  of  the  most  difficult  tasks  of 
the  novice,  are  especially  pertinent  and  are  expressed  in  a  fair  and 
conservative  manner. 

The  book  is  so  complete  that  it  can  be  put  in  the  hands  of  a 
young  engineer  with  confidence  that  it  will  enable  him  to  make  re- 
liable tests  on  cement.  The  wealth  of  photographs  and  line  cuts 
furnish  the  pictorial  examples  of  how  to  conduct  cement  tests,  and 
the  300  pages  of  text  are  so  explicit  that  even  the  most  inexperienced 
man  can  soon  learn  the  art  of  cement  testing.  Yet  the  book  has  not 
a  superfluous  paragraph.  The  list  of  chapters  includes:  (1) 
Classification  and  Statistics,  (2)  Composition  and  Constitution,  (3) 
Manufacture,  (4)  Inspection  and  Sampling,  ,(5)  The  Testing  of 
Cement,  (6)  Specific  Gravity,  (7)  Fineness,  (8)  Time  of  Setting, 
(9)  Tensile  Strength,  (10)  Soundness,  (11)  Chemical  Analysis,  (12) 
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(15)  Other  Varieties  of  Cement  than  Portland,  (16)  Specifications, 
The  Author's;  (Am.  Soc.  C.  E.;  Am.  Soc.  Test.  Mtls.;  Soc.  Chem. 
Indust.;  Corps  Eng.  U.  S.  A.;  British  Standard;  Can.  Soc.  C.  E.) 

Cloth,  6x9  inches;  330  pages;    142  illustrations;   58  tables; 
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